Thirty-two female patients with clinical and urodynamic findings of genuine stress urinary incontinence were evaluated before and 6 months after surgery for stress urinary incontinence. Twenty-nine control patients had identical evaluations before and 6 months after surgery which did not involve the urethrovesical junction. Twenty-four patients with primary bladder instability had similar evaluations and served as a second control group. Anatomical landmarks indicating support to the urethrovesical junction were evaluated by the position of the urethra at the most dependent point in the bladder on straining and the urethral descent on straining to beneath the posterior ramus of the symphysis pubis on bead chain cystography. The urethrovesical junction drop on straining was evaluated by transrectal ultrasonography. Cystographic and ultrasonographic tests for the position of the urethrovesical junction at the most dependent position in the bladder during straining were very sensitive in women with stress urinary incontinence (94 and 87% respectively) but much less specific (45 and 48% respectively). When evaluating anatomical support to the urethrovesical junction and its descent on straining, these tests were both highly sensitive (97 and 94% respectively) and specific (76 and 96% respectively) in women with genuine stress urinary incontinence. Simple clinical tests for support of the urethrovesical junction, such as the Q tip test, are non-specific in patients with stress urinary incontinence. Transrectal ultrasonography is a simple and quick out-patient procedure. The availability of ultrasound equipment in most clinics and the high sensitivity and specificity of the test make it an attractive and cost-effective alternative to X-ray cystography in the pre-operative evaluation of anatomical support to the urethrovesical junction.