To determine if previously breast fed children are more or less likely to have developed juvenile rheumatoid arthritis (JRA). Reports suggest that non-breast fed children are more likely to develop certain diseases for which an autoimmune pathogenesis is suspected. Data from a longitudinal, case controlled population survey of childhood rheumatic diseases in Saskatchewan, Canada, included information pertaining to breast feeding history. These data were analyzed in the context of a retrospective, case controlled study to confirm results of an earlier report in which JRA was found to occur less frequently in previously breast fed children. For this analysis a child who had been breast fed for any length of time was categorized as having been a breast fed subject. A population of 88 children with pauciarticular JRA were more likely than an unmatched control population of 331 healthy children (p = 0.01) or those with polyarticular JRA (p = 0.006) to have been breast fed. However, when corrected for the number of comparisons made, statistical significance was not achieved 49 children with polyarticular JRA did not have a breast feeding history significantly different from the unmatched control population. In a retrospective, case control analysis of 54 children with pauciarticular JRA and 23 children with polyarticular JRA, no significant differences were noted when the JRA populations were compared to the parent selected, matched control populations (odds ratio for pauciarticular JRA 2.17: confidence interval 0.87-5.44; p = 0.06 and for polyarticular JRA 1.17: CI 0.33-4.20: p = 0.78). These results do not indicate a strong relationship between antecedent breast feeding and the subsequent onset of JRA and fail to confirm the results of earlier analyses in which JRA was found to occur more frequently in children who had not been breast fed.