A self-administered patient questionnaire was developed to assess the severity of key symptoms before and after transurethral prostatectomy (TURP). This questionnaire was validated by comparison with a standard assessment performed by the doctor. Complete data were obtained on 39 men studied before and 3 months after prostatectomy. Close associations were found between the scores resulting from the assessments performed by the patient and those carried out by the doctor. These associations were found for individual scores and for aggregate scores for obstructive and irritative symptoms before and after operation. Symptom scores after operation were significantly related to the patients' overall assessment of whether the operation had been a success--a low score being associated with a satisfactory outcome. It is suggested that self-administered symptom questionnaires can give a reliable picture of the outcome of prostatectomy and might be useful in developing audit systems.