The relationship between lumbar sagittal mobility and symptoms was explored in a 1-year prospective study of 55 patients undergoing manipulative treatment. A significant increase in mean mobility was found to occur in the 1st month, together with a concomitant significant decrease in mean pain values; symptoms continued to decrease thereafter, but mobility remained unchanged. More detailed analysis of the data revealed that symptomatic improvement was as common in patients with unaltered or reduced mobility as it was in those who showed an increase; changes in mobility at 1 month had no predictive value for symptomatic status at 1 month or 1 year. It is concluded that if any benefits actually result from manipulative therapy they are not a direct function of increased overall lumbar sagittal mobility. It remains possible that manipulation may influence other mobility parameters, such as coupled motions, so future studies should be directed toward investigation of three-dimensional movement patterns.