One hundred forty-eight consecutive cases of scrotal pain and swelling in boys under the age of 16 have been reviewed. Eighty-nine of these suffered from torsion, either of the testis or appendix testis. Similarity in clinical history and physical findings makes differentiation of torsion from epididymo-orchitis difficult. Operation in all appears to be the only safe treatment. Delay in operation is disastrous with no testicular salvage after 24 hours. On the other hand, 17 of 19 operated upon on the day of onset of symptoms had viable testes.