Several scales exist for measuring functional status in patients with low-back pain (LBP). There are few comparative data, however, to suggest which scales may perform best. We compared the Sickness Impact Profile (SIP), its major subscales, and a short index derived from the SIP (a slight modification of an index proposed by Roland) with regard to reliability, validity, and sensitivity to change. Walk-in patients with mechanical LBP (n = 136) completed the entire SIP at an index visit and again 3 weeks later. The examination of individual items allowed scoring for the derivative scales. The modified Roland Scale appeared to have reliability, validity, and sensitivity that were at least as good as the overall SIP or its major subscales. Although the Roland Scale did not measure psychosocial function well, this aspect of functioning changed less over time than physical function.