To assess the causative role of non-sporing anaerobes in cass of erosive balanoposthitis, anaerobic culture was performed on purulent discharges from 104 patients with penile ulceration, a foul-smelling discharge, and a mixed and motile bacterial flora. Most of 29 culturally confirmed infections were due to mixed anaerobes and eight to single anaerobes. A rapid response to treatment with metronidazole also confirmed the anaerobic cause of the infection. Thus, acute anaerobic balanoposthitis can be readily diagnosed clinically and is easily treated.