To assess the sensitivity of the Arthritis Impact Measurement Scales (AIMS), we analyzed data from 3 clinical trials. One trial involving 255 patients with rheumatoid arthritis (RA) was a 12-week, randomized controlled trail of diclofenac, naproxen, and aspirin. Two trials were open-label studies of 24 weeks duration that included 165 RA and 355 osteoarthritis (OA) patients, all of whom were treated with diclofenac. In addition to the AIMS, tender joint count, morning stiffness, and erythrocyte sedimentation rate were used as outcome measures in the trials. The AIMS results showed substantial improvements in Physical Function, Psychological Status, and Pain, as well as in overall Arthritis Impact. These improvements were detected by the time of the initial outcome assessment at 4 weeks or 8 weeks, and were detected in patients with either OA or RA. These AIMS results closely parallel improvements shown by traditional clinical measures, and demonstrate that the AIMS health status measure is sensitive to improvements in OA as well as in RA. The AIMS also detects responses produced by therapy with nonsteroidal antiinflammatory drugs (NSAIDs), and these improvements can be demonstrated in as short a treatment time as 4 weeks. These findings confirm the utility of the AIMS for assessing outcome in rheumatic disease studies, and they have implications for the design of future clinical trials of NSAIDs.