To determine if children with juvenile rheumatoid arthritis (JRA) are less likely to have been breast fed than controls. Case-control study of data obtained from a survey of mothers 54 children with JRA and 79 playmates regarding breast feeding. Duration of breast feeding was tabulated and odds ratios (OR) with 95% confidence intervals (CI) were determined. OR for breast feeding in children with JRA was 0.40 (0.20-0.81, 95% CI) compared to playmates. For pauciarticular JRA (N = 28) OR was 0.31 (0.10-0.93); in polyarticular JRA (N = 24) OR was 0.60 (0.21-1.70). Lower OR for increased durations of breast feeding were noted in children with JRA. Children who have had JRA, especially pauciarticular JRA, are less likely to have been breast fed than controls, suggesting that breast feeding may have a protective effect on the development of JRA.