During 1983-86, genital herpes (GH) was diagnosed in 225 (19%) of 1194 patients attending the STD clinic, attached to a Medical College in south India. The patients included 169 men and 56 women; 50 had primary GH and 175 had recurrent GH. The prevalence of GH in men and women did not differ significantly but the proportion of primary GH was significantly higher in women. There was no seasonal variation. The clinical epidemiology of these patients is compared with those in other countries. Virological confirmation of GH was obtained in 38 per cent of patients through culture and in a further 12 percent through serological tests. Papanicolaou smears were positive in 30 per cent men regardless of the type of GH, and in 38.5 and 7.1 per cent women with primary and recurrent GH, respectively. Cultures were positive for herpes simplex virus (HSV) in 38.7 per cent of patients with primary and 38.2 per cent with recurrent GH. Among the 52 viral isolates typed, nine of the 10 isolates from primary GH and all 42 from recurrent GH, were HSV-2. The geometric mean titres of antibody against HSV were higher in patients than in controls.