An easy-to-use “A” mode ultrasonic device to determine residual bladder volumes has been fabricated and tested. Small bladder sections are identified by inspecting “A” scans for bladder characteristics such as an echo-free urine area, depth of the potential bladder section, and height and width of the far wall echo. Bladder volumes are estimated to within 50 cc. Data from 37 subjects showed an average difference between calculated and measured volumes of −1.9 cc and a standard deviation of 28 cc. Measured volumes were obtained by either catheterization (patients) or urination (normal volunteers).