The purpose of this study was to investigate whether the maneuver of altering the angle of pelvic tilt when standing is effective in changing the angle of lumbar lordosis. The importance of the study was to establish a scientific basis for a common clinical assumption. Pelvic tilt and lumbar lordosis were measured during three conditions: with subjects in a normal standing posture, with subjects assuming a maximal anterior pelvic tilt posture, and with subject assuming a maximal posterior pelvic tilt posture. Measurements of pelvic tilt and lumbar lordosis were obtained using a television/computer system that obtained the three-dimensional coordinates of markers on the pelvis and spine at 20-msec intervals. Each measurement was made three times, and all were found to be reliable, with intraclass correlation coefficients (3,1) ranging from 0.78 to 0.95 (p < 0.001). Adopting a maximal anterior pelvic tilt changed the pelvic attitude relative to the horizontal by an average fo 11.4 degrees (p < 0.001) and increased the lumbar lordosis by an average of 10.8 degrees (p < 0.001). Adopting a maximal posterior pelvic tilt changed the pelvic attitude by an average of 8.7 degrees (p < 0.001) and decreased the lumbar lordosis by an average of 9.0 degrees (p < 0.001). The results of this study demonstrate that altering the pelvic tilt significantly changes the angle of lumbar lordosis. This lends support to the use of pelvic tilting exercises to increase or decrease the degree of lumbar lordosis, at least for the duration of the exercise.