Seventy-five men with gonococcal urethritis were treated with a single oral dose of thiamphenicol, and 88 men with this infection were treated with two 1.5-g oral doses of lymecycline taken 12 hr apart. Of the 75 subjects treated with thiamphenicol, 72 (96%) were cured, as compared with 80 (91%) treated with lymecycline. Sixty subjects (37%) were infected with penicillinase-producing Neisseria gonorrhoeae. In this group, 28 (97%) of 29 subjects treated with thiamphenicol were cured, as compared with 29 (94%) of 31 subjects treated with lymecycline. Patient compliance with the two-dose regimen was excellent, and no adverse effects occurred with either drug. Lymecycline may therefore be an effective alternative to thiamphenicol in those countries where strains of N. gonorrhoeae remain sensitive to the tetracyclines.