Prompt diagnosis of testicular torsion remains difficult. Since warning symptoms occur in one third of patients and salvage rates correspond to the interval between symptom onset and operation, higher salvage rates should be achievable. Separating torsion from epididymitis is complicated by overlapping ages of peak incidence, shared symptoms, and the need for rapid distinction of the two. Doppler studies (88% accuracy) and nuclear scans (95% accuracy) help confirm the diagnosis, but correct technique is essential, and their use should not delay prompt operation. The diagnosis of epididymitis should be made cautiously in persons younger than the age of 35 years. (JAMA 1983;249:2522-2527)