A new device is described to measure clinically the softness of the female urethra. It is a rod-shaped urethral sound with a longitudinal groove along its surface. The sound is constructed in sizes 12 to 24 French. Each has one groove which is 2 mm wide and either 2, 2.5, or 3 mm deep. The groove is 11 cm long. When inserted into the filled female bladder per urethram, the groove will span the urethra from the bladder to the outside. If the urethral inner lining is soft and deformable, it will fill itself into the groove and prevent leakage of urine from the bladder along the groove to the outside. If the urethra is relatively rigid, urine will leak from the bladder. This instrument permits testing of women to determine urethral properties in preventing leakage when studied with a range of probe sizes.