The objective of this study was to assess the validity and responsiveness of a new quality of life instrument, the Patient Generated Index (PGI), in patients with rectal cancer. Thirty-three patients with rectal cancer were administered the PGI, the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaires QLQ-C30 and QLQ-CR38, and the Medical Outcomes Study short form SF-36 questionnaire preoperatively and at 3 months postoperatively. The PGI was assessed in this group of patients for validity and responsiveness. PGI scores achieved significant correlations with a number of domains on the three quality of life (QOL) questionnaires. Stepwise regression analysis showed that 91.3% of the variation in PGI scores could be explained by three health-related QOL variables alone: pain, role limitations due to physical problems, and a global rating of health and QOL. The mean PGI score showed significant improvement 3 months following surgery. The PGI was found to be more responsive to change than the SF-36, the QLQ-C30, or the QLQ-CR38 items except the micturition item. The PGI assesses the extent to which the expectations of patients suffering from rectal cancer are matched by reality; and it satisfies the criteria of validity and responsiveness of this instrument for this cancer. Further studies are needed to determine its psychometric properties in other areas of surgery and oncology. If these studies support our findings, we believe that patient-centered measures such as the PGI may provide a meaningful assessment of the outcome of surgery for patients with cancer.