Historical, physical, and laboratory findings in 36 patients with surgically proven torsion of the spermatic cord or testicular appendages are reviewed. These patients were seen in a large metropolitan hospital during a recent 11-year period. Each year, an average of 3.2 patients with torsion have been seen, or one for each 5,728 hospital admissions. The average yearly census of patients treated by the urological service during the same period was 2,615, an average of one patient with torsion for each 503 admissions. Torsion may occur at any age but certainly predominates during the adolescent years (85% to 90%). The salvage rate of the testicle, in 28 patients with acute torsion, was 25%. Forty-three percent of patients with acute torsion were initially thought to have epididymitis, with loss of the affected testicle in all cases. The treatment is immediate surgical exploration of the affected organ and orchiopexy of the opposite testis.