Abstract "Clinical and Biological Progresion of Incidental Prostatic Cancer (Stage t1a)" Objetives To analyze the biological and clinical progression of the prostate cancer stage T1a. Material and Methods Retrospective study of 44 patients diagnosed of T1a prostate carcinoma between 1985 and 2001. We value biological and clinical progression, time up to the progression, mortality for tumour reason and survival, with the following stratification: patients without initial treatment and patients treated by means of external radiotherapy or radical prostatectomía. Results Of all 44 patients biological progression was observed in 5 (11.36%) and clinical progression in 4 (9.09%). The mortality to 5 years for tumour reason was of 2 (4.54 %). Of all 38 patients without initial treatment biological progression was observed in 5 (13.15%), in an average time of 25.8 months and clinical progression in 4 (10.52%), in an average time of 34.5 months. The mortality to 5 years was of 2 (5.26%). In all 6 patients to whom radical treatment carried out them progression was not observed and they all live. There are no statistically significant differences between both groups of patients (p = NS). Conclusions The biological and clinical progression of the T1a prostate cancer is low, 11.36% and 9.09%, respectively. The mortality to 5 years is of 4.54%. Differences of survival do not exist, statistically significant, between treated and not trated.