A major concern in school screening programs as well as in the clinical assessment of spinal curvature has been the frequent radiation exposure required to ascertain curve progression. Various techniques have been developed to identify scoliosis such as the Moire and ISIS techniques, but these are very sophisticated and expensive. The authors have developed a simple procedure of identifying and documenting spinal curvature during the performance of the Adams forward bend test, using an ultrasonic sound probe, four sound receivers, and a micro-computer. The probe is run along the spinous processes emitting an ultrasonic sound, which is picked up by four receivers mounted at the corners of a rectangle above the patient. The signal is fed into a micro-computer and the spinal curvature is plotted out. The magnitude of the curve is calculated by the computer, and the actual curve plus the magnitude is printed in hard copy to be placed in the chart. The reproducibility error and intermeasurer error has been less than 5%. A series of 30 patients with varying magnitudes of scoliosis from 15 degrees to 73 degrees were examined. The results of the ultrasonic digitization were compared with standard scoliosis radiographs of the patient taken the same week. The average curvature measured from the radiographs was 38 degrees, and from the ultrasonic digitization technique, 30 degrees: The forward bend position contributed to smaller curvature measurement, and measurement in the standing position was thought to be a better technique. Ultrasonic digitization as a method of curve measurement is most accurate in curves over 30 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)