In 141 male urological patients, age ranged from 10 t o 76 years old, temperature of rectum, testicle, scrotal cavity and external inguinal ring region was measured by means of a hypodermic needle with a thermistor device. The patients were in operation room, kept quitely at supine position, mainly under spinal or general anesthesia, and their trunk and lower extremities were draped with cotton sheet but the external genital area was exposed to air. Room temperature was recorded at the same time with a mercury thermometer. Statistical analysis was made on records of every area. Out of the 141 cases studied, 111 cases were considered to be normal testicular group since their illnesses were not supposed to have effect directly on testicular temperature, and the remaining 30 cases were tentatively classified as abnomal testicular group because their illnesses originated in or around the testicle with possibility that the illness gave direct influence on testicular temperature. I. Normal testicular group : (1) Normothermic group (incl uding 83 cases in which rectal temperature ranged between 36.2 and 37.6°C) demonstrated that their rectal temperature was 37.0±0.05°C, testicular temperature 33.1±0.12°C in the right side and 33.2±0.13°C in the left, scrotal cavity temperature 32.6±0.12°C in the right and 32.6±0.12°C in the left and external inguinal ring region temperature 34.7±0.10°C in the right and 34.8±0.09°C in the left. Hyperthermic group (consists of 18 patients whose rectal temperat u re was above 37.7°C) showed that their rectal temperature was 38.2±0.10°C, testicular temperature 34.5±0.28°C in the right and 34.5±0.27°C in the left, scrotal cavity temperature 34.0±0.26°C in the right and 33.9+0.26°C in the left and external inguinal ring region temperature 35.8±0.18°C in the right and 35.8±0.21°C in the left. Hypothermic group (consists o f 10 cases in which rectal temperature was below 36.1°C) gave results of rectal temperature being 35.8±0.06°C, testicular temperature 32.3±0.20°C in the right and 32.3±0.18°C in the left, scrotal cavity temperature 31.8±0.17°C in the right and 31.8±0.18°C in the left and external inguinal ring region temperature 33.6±0.18°C in the right and 33.6±0.18°C in the left. (2) Between the normothermic and hyperthermic groups, average differences in temperature of rectum, testicle, scrotal cavity and external inguinal ring region were found to be 1.19°C, 1.40-4.30°C, 1.34-1.31°C and 1.14-X1.05°C respectively. Between the normothermic and hypothermic groups, they were 1.15°C, 0.86-0.87°C, 0.87-0.83°C and 1.12-1.18°C respectively. Between the hyperthermic and hypothermic group, they were 2.34°C, 2.26— 2.17°C, 2.16-2.14°C and 2.26-2.23°C respectively. These difference were statistically significant at the level of the risk below 1 %. (3) In every, groups, average differe nces between the right and left testicular temperature, between the right and left scrotal cavity temperature and between the right and left external inguinal ring region temperature were all found to be less than 0.14°C and statistically not significant at all. (4) In the normothermic, hyperthermic and hypothermic groups, differences in temperature between rectum and testicle were 3.8-3.9±0.11°C, 3.7±0.28~0.29°C and 3.5±0.17-0.19°C respectively, between rectum and scrotal cavity, were 4.4±0.11°C, 4.2~4.3±0.26-0.27°C and 4.0±0.16-0.19°C respectively, between rectum and external inguinal ring region, were 2. 32.2±0.08-0.09°C, 2.4±0.16-0.20°C and 2.2±0.19~0.20°C respectively, between testicle and scrotal cavity, were 0.5-0.6±0.04°C, 0.5-0.6±0.11-0.08°C and 0.5-0.6±0.11--0.13°C respectively, between external inguinal ring region and testicle, were 1.6±0.08-0.09°C, 1.3±0.21 —0.16°C and 1.3±0.24-0.20°C respectively, while between external inguinal ring reg ion and scrotal cavity, were 2.1-2.2±0.09°C, 1.8-1.9±0.18-0.17°C and 1.8±0.17-0.16°C respectively. These figures are statistically significant at the level of risk below 0.1 % except the difference between testicular and scrotal cavity temperature. (5) In the normothermic group, average dif ference in temperature of rectum, testicle, scrotal cavity and external inguinal ring region between the age groups of 10 to 20 years and 30 to 40 years was 0.16-0.45°C which was not statistically significant. On the contrary, average differences in temperature of rectum, testicle, scrotal cavity and external inguinal ring region between the age groups of 10 to 20 and above 50 years were 0.38°C, 0.99-1.17°C, 0.80-0.79°C and 0.87,-0.79°C respectively, and between the age groups of 30 to 4 0 and above 50 years, were 0.38°C, 0.58-0.72°C, 0.62-0.55°C and 0.71-0.58°C respectively. These figures indicated that temperatures of these areas are lower in the advanced age groups than younger groups and showed statistically significant differences at the level of risk below 5 %. (6) In 111 cases, correlativities were determined between room temperature a nd rectal and scrotal cavity temperatures, rectal and testicular temperatures, scrotal cavity and and external inguinal ring region temperatures and testicular and scrotal cavity temperatures. The results showed almost complete positive correlation between testicular and scrotal cavity temperatures, moderately positive correlations between scrotal cavity and room temperatures and between scrotal cavity and rectal temperatures, but almost no correlation between rectal and room temperatures. (7) In 10 cases, of whic h age ranged from 28 to 75 years, the exposed external genital area was entirely draped with cotton sheet. The testicular temperature has risen, from the mean of initial temperature of 32.7°C (30.8-33.9°C), up to the mean of 34.3°C (32.4-35.9°C) in about 20 minutes after the draping. Removal of the sheet made the testicular temperature descended down to the mean of 32.6°C (31.0-33.8°C) in about 20 minutes. During these procedures, rectal temperature altered from the mean of 37.1°C (35.5-39.1°C) to 36.9°C (35.4-39.0°C). This experiment confirmed that testicular temperature will be varie d at the mean range of 1.6°C (0.8-2.3°C) by draping or exposing the external genital area. II. Abnormal testicular group (tentatively called) : (1) In 8 cases of chronic epididymal tuberculosis, no statistically significant difference in temperatures at every area tested from that of normal testicular group was demonstrated. This disease, therefore, was thought to have no effect on testicular temperature . (2) In 8 cryptorchid cases (testis located in the inguinal canal), the rectal, testicular, scrotal cavity and external inguinal ring region temperatures were 37.3±0.07°C, 35.7± 0.36°C, 34.9±0.18°C and 35.1±0.08°C respectively in 6 testes of the normothermic group and 38.1±0.26°C, 36.9±0.40°C, 36.1±0.26°C and 36.2±0.26°C respectively in 2 cases of the hyperthermic group. In each group, the testicular temperature was 2.6-2.4°C higher than that of in normal testicular group. This difference was found to be statistically significant. (3) In 3 cases of left spermatic varicocele, all of which belonged to hyperthermi c group, the temperatures of various areas tested have not differed from that of in normal testicular group. (4) In a case of left embryonal cancer (hen's egg-sized), only the tumor-bearing testis showed higher temperature, 36.3°C, than normal group, but the other areas tested showed similar temperature as that of normal testicular group. In a case of right teratoma (human fist-sized), however, the temperatures of not only the tumor-bearing testis but of the other healthy testis and scrotal cavity were higher than that of normal testicular group. Same phenomenon were seen in a case of left intra-scrotal hematoma. (5) In 3 cases of hydrocele, 2 cases of spermatocele, 2 cases of testicular atrophy and a case of aplasia of spermatic duct, the temperatures of all areas tested were not statistically different from that of normal testicular group.