Neural stimulation of the sacral nerve roots could become an acceptable and promising modality in controlling variable forms of difficult voiding dysfunctions. A total of 50 patients who presented with various forms of voiding dysfunction underwent initial screening by percutaneous nerve evaluation of the S3 nerve root guided by movements of the levator ani and toes. Only 17 patients demonstrated a satisfactory response to percutaneous nerve evaluation and subsequent subchronic wire testing for 4 to 5 days, and they were eligible to enter the study. The studied patients (13 women and 4 men) were classified into 2 groups according to presentation. Group 1 included 8 patients who presented mainly with nonobstructive chronic urinary retention. All 8 patients were on intermittent self-catheterization except 1 with a suprapubic tube. The 9 patients in group 2 mainly presented with other forms of voiding dysfunctions, including pain (suprapubic and perineal), frequency and/or urgency. All patients were neurologically free, and had failed pharmacological and surgical attempts to correct the problems. In both groups radiological and ultrasound evaluations of the urinary tract as well as cystourethroscopy were within normal limits. Urodynamic studies were performed preoperatively and postoperatively. Unilateral S3 foramen implantation was performed on the selected side in all patients. Followup ranged from 3 to 52 months. All patients were followed preoperatively and postoperatively by voiding and itemized symptom score diary as well as a quality of life questionnaire. Each symptom and question were given certain grades that reflect the severity or importance to the patient. The symptom scores and the quality of life questionnaires were analyzed preoperatively and postoperatively. In group 1 voided volume (expressed as a percentage of total bladder capacity) was significantly increased at 6 months (23 +/- 7.5% preoperatively versus 81.9 +/- 7.7% postoperatively, p < 0.05) and, accordingly, residual volume (also expressed as a percentage of total bladder capacity) was significantly decreased. The maximum flow rate increased to 18.0 +/- 2.6 ml. per second postoperatively compared to 7.8 +/- 3.1 ml. per second preoperatively. The number of intermittent self-catheterizations per day decreased to 1.3 +/- 0.8 compared to 4.2 +/- 0.6 preoperatively (p < 0.05). Uninhibited bladder contractions with vesicosphincteric dyssynergia disappeared in 1 patient, while they persisted in 1 for up to 6 months. In group 2 the average improvement in pain and difficulty to start voiding was 85%, frequency improved by 37%, urgency by 42%, and leaking episodes and number of diapers per day decreased by 50%. Uninhibited bladder contractions disappeared in 1 patient within 6 months.(ABSTRACT TRUNCATED AT 400 WORDS)