Forty-seven women had urethral pressure profile determinations performed at rest and during a Kegel pelvic muscle contraction, after brief standardized verbal instruction. Twenty-three (49%) had an ideal Kegel effort--a significant increase in the force of urethral closure without an appreciable Valsalva effort. Twelve subjects (25%) displayed a Kegel technique that could potentially promote incontinence. Age, parity, weight, estrogen deprivation, prior continence surgery or hysterectomy, and passive urethral function did not predict a successful effort. We concluded that simple verbal or written instruction does not represent adequate preparation for a patient who is about to start a Kegel exercise program.