The purpose of this study was to assess the effects of two different treatment modalities on the rehabilitation process of chronic sacroiliac joint patients. The treatment modalities included spinal manipulative therapy given by a chiropractor and a program of back school therapy given by a physiotherapist. The rehabilitation process was assessed using clinical and biomechanical measures. It was found that back school therapy was a better treatment modality than the spinal manipulative therapy, according to the clinical measures of rehabilitation. Precisely the opposite result was found for the biomechanical measures.