Females (34) with sensory urge incontinence were treated with phenylpropanolamine, 50 mg twice daily, and in some cases alternatively with placebo. Subjective effect of the treatment was reported in 22 of the 34 patients, in only 3 cases of 15 was a similar good response achieved with placebo. Objectively no significant difference in maximum urethral pressure or in functional urethral length was found after treatment. Maximal bladder volume was markedly increased in 4 cases. There were no cases with uninhibited bladder contractions. Compliance before and after treatment was normal. The most conspicuous objective finding urodynamically was a stabilization of the condition described as unstable urethra, where the urethral pressure variation repeatedly exceeded 15 cm H2O. This stabilization was observed in 11 out of 14 cases with this condition in whom the clinical effect was reported as good.