A case of trichomonas vaginalis infection involving the median raphe of the penis is presented. The infection was contracted after sexual exposure. The patient had no urethral discharge but had a penile swelling tht discharged pus. Microscopic examination and culture of the discharge showed the presence of T. vaginalis. Treatment with metronidazole (250 mg thrice daly for seven days) eradicated the infection, but the swelling remained and a cyst was excised. One month after the surgical procedure, the patient was clinically normal and cured of the infection.