A symptom index for benign prostatic hyperplasia (BPH) was developed and validated by a multidisciplinary measurement committee of the American Urological Association (AUA). Validation studies were conducted involving a total of 210 BPH patients and 108 control subjects. The final AUA symptom index includes 7 questions covering frequency, nocturia, weak urinary stream, hesitancy, intermittence, incomplete emptying and urgency. On revalidation, the index was internally consistent (Cronbach's alpha = 0.86) and the score generated had excellent test-retest reliability (r = 0.92). Scores were highly correlated with subjects' global ratings of the magnitude of their urinary problem (r = 0.65 to 0.72) and powerfully discriminated between BPH and control subjects (receiver operating characteristic area 0.85). Finally, the index was sensitive to change, with preoperative scores decreasing from a mean of 17.6 to 7.1 by 4 weeks after prostatectomy (p < 0.001). The AUA symptom index is clinically sensible, reliable, valid and responsive. It is practical for use in practice and for inclusion in research protocols.