Thirty women with combined urinary stress incontinence and detrusor instability were treated by a colposuspension operation for urinary incontinence. Following surgery we found a significant reduction of symptoms regarding detrusor instability, from 22/30 patients preoperatively (73.3%) to 10/30 patients (33.3%). Urodynamically, 40% of the patients had detrusor instability following surgery. Only one surgical failure was encountered (3.3%). It is suggested that patients with combined detrusor instability and stress incontinence should be operated on. This group of patients was cured as far as stress incontinence is considered, and 60% of the patients presented normal cystometric findings and more than 50% of the patients (12/22) greatly improved clinically, regarding symptoms of detrusor instability, following surgery.