Ninety-seven patients with 118 sites infected with Neisseria gonorrhoeae were treated with a single dose of either procaine penicillin G (4.8 x 10(6) U) or cefotoxime (1.0 g) intramuscularly. Only the penicillin group took 1 g of probenecid orally. The numbers of infected sites in each treatment group were as follows: penicillin-urethra, 37; rectum, 9; cervix, 8; and pharynx, 4; cefotaxime-urethra, 42; rectum, 9; cervix, 5; and pharynx, 4. The cure rates in each treatment group were 100%. No adverse reactions were noted in either group. beta-Lactamase-positive N. gonorrhoeae strains were not found. Ninety-five percent of clinical isolates were inhibited by less than or equal to 0.007 micrograms of cefotaxime and less than or equal to 0.25 micrograms of penicillin per ml. In this study cefotaxime was as effective as procaine penicillin in the treatment of uncomplicated gonorrhea.