In a study of 151 male patients attending a sexually transmitted disease clinic, 40 (26.4%) had non-gonococcal urethritis. Herpes simplex virus was isolated in tissue culture of HEp-2 cell line from 10 of the patients with non-gonococcal urethritis, and identified by complement fixation and indirect immunofluorescent anti body tests. Of the isolates, 30% were Herpes simplex virus type 1 (HSV-1), while 70% were Herpes simplex virus types (HSV-2).