We examined the ability of the Snap-Gauge band to differentiate rigid from nonrigid erections in men complaining of impotence. A total of 80 patients was measured by a Snap-Gauge band and via technician assessment of erectile rigidity while undergoing nocturnal penile tumescence testing. The Snap-Gauge band correctly diagnosed 77.5 per cent of the patients with a sensitivity of 70 per cent and specificity of 80 per cent. The Snap-Gauge band is inexpensive compared to sleep laboratory testing and it is relatively reliable. We conclude that the Snap-Gauge band has a role in impotence assessment and it can function as a screening device in evaluation of this problem.