The influence of patterns of usage on the structure and function of the hands was formally tested. Three groups of female textile workers, each employed in a distinct and defined, atraumatic, repetitive, stereotyped manual task for at least 20 years, were identified in a single rural mill. Replicate data were obtained for the following measures of structure and function: range of motion, a score for the degree of radiographic degenerative changes at each hand joint, malalignment at digital joints determined radiographically, and a quantitative measure of osteophyte formation. Significant and consistent differences in the right hand when compared to the left were detected. Furthermore, highly significant task-related differences were demonstrated. These task-related differences in the structure and function of the hands were consistent with the pattern of usage. Therefore these three patterns of usage influence hand structure and function in the population studied.