A 24 year old man presented with intense acute pain in the genital area following intercourse. Clinical examination revealed extensive edema of the scrotum, and use of a light source produced dark transillumination, excluding the diagnosis of a testicular cyst which would give clear transillumination. Palpation of the area revealed no masses or lesions suggesting a tumor. The photograph, taken after the start of treatment, shows clearly the extensive hemorrhage. Knowledge of the hemorrhagic diathesis and the therapeutic effect of administration of antihemophiliac factor confirmed the diagnosis.