A total of 40 mature or aged rams with spontaneous varicocele detected by scrotal palpation were subjected to detailed necropsy examination. Varicocele was bilateral in 22 rams or was located on the left or right sides only, in 8 and 10 rams, respectively. This distribution contrasted with varicocele in man in which the left side is involved in 70 to 100% of cases. Mean sizes of varicoceles in mm (length x diameter) were 117 x 46 and 104 x 45 for the left and right sides, respectively, and they were located high in the pampiniform plexus, approximately 100 mm from the dorsal pole of the corresponding testis. All varicoceles were thrombosed. Changes associated with large varicoceles included testicular mineralisation and occluding thrombosis of testicular vessels. Total testis weight-bodyweight ratio in rams with varicocele (5.8 to 6.4 x 10(-3] was significantly less (P less than 0.05) than in normal (control) rams from the same flocks (7.9 x 10(-3] suggesting that some degree of testicular atrophy resulted from presence of a varicocele.