A group of 50 men with uncomplicated gonococcal infections were treated with single, oral doses of 2.5 g of thiamphenicol. Reexamination, which included culture for Neisseria gonorrhoeae, was performed three to four days and seven days after treatment. Thirty-two (91%) of 35 men with urethral infections, 13 (87%) of 15 with rectal infections, and four (57%) of seven with pharyngeal infections were cured. None of the men from whom N. gonorrhoeae was reisolated admitted further sexual exposure. Treatment failure did not correlate with decreased sensitivity of the isolates to thiamphenicol in vitro. Three men had urethral infections with Chlamydia trachomatis before therapy, and the organism was reisolated after therapy in every case. No hematologic abnormalities occurred in any of the 50 patients treated with thiamphenicol, but 13 (26%) developed adverse gastrointestinal symptoms.