Health services researchers frequently must choose between a generic health status measure, such as the Sickness Impact Profile (SIP) and a disease specific health status measure, such as the Arthritis Impact Measurement Scales (AIMS). In a longitudinal study of patients with knee or hip osteoarthritis, we examined the extent to which these 2 measures provide similar information. We found the SIP and AIMS to be significantly (p less than 0.001) correlated for physical (0.75-0.76) and total health (0.70-0.73). Correlations for psychological health were statistically significant, albeit modest (0.37-0.40). We conclude that, for most dimensions, investigators will obtain similar information using either well validated instrument.