The aims of this study were to determine the frequencies of infection with Neisseria gonorrhoeae at various sites in homosexual men who were attending clinics for treatment of sexually transmitted diseases in central Scotland and to appraise the diagnostic tests used. Specimens for culture were taken from the urethra, pharynx, and anorectum of every homosexual man in the study. When the first cultures of pharyngeal and rectal specimens were negative, these cultures were repeated twice at weekly intervals. The urethra was infected in 169 (60.8%), the anorectum in 114 (41.0%), and the pharynx in 23 (8.3%) of 278 patients who had gonorrhea. By reliance on only one set of tests, eight (7.0%) of 114 patients who had rectal gonorrhoea and six (26.1%) of 23 patients with pharyngeal infection would have been missed. The results indicate the importance of obtaining specimens for culture from all sites that might possibly be infected, regardless of the symptoms.