OBJECTIVE To assess the accuracy of radionuclide scrotal imaging (RSI) in the diagnosis of testicular torsion and torsion of testicular appendages. METHODS Eighty-seven patients (mean age 30.1 years, range 8-65) who presented with acute scrotal pain were evaluated by RSI and the results correlated with the clinical and surgical findings. RESULTS Of the 87 patients, 44 underwent scrotal exploration and 42 patients were treated conservatively. One patient with a 'missed torsion' pattern on RSI refused operation and was lost to follow-up. Of the 44 patients who underwent surgery, testicular torsion was found in 30 and torsion of testicular appendages in 14 patients. The specificity of the RSI in diagnosing testicular torsion was 100% and the sensitivity was 98%. An area of increased tracer activity in the presence of a normal radionuclide angiogram was suggestive of torsion of testicular appendages with a specificity of 93%. Of the 42 patients who were treated conservatively, 19 had epididymitis, according to clinical and RSI findings, 10 had torsion of testicular appendages, two had orchiepididymitis, two had hydrocele, two had haematocele and seven patients had normal testes. At a follow-up examination, normal testicles were found in all 42 patients. CONCLUSIONS The RSI may assist in the evaluation of nontraumatic acute scrotum, and can clearly distinguish among testicular torsion, torsion of testicular appendages and epididymitis.