OBJECTIVE To study the relationship between bone mineral loss and disease subtype, disease duration and corticosteroid use in children with juvenile chronic arthritis (JCA). METHODS Bone mineral density (BMD) was evaluated by dual X-ray absorptiometry (DXA), using a Hologic QDR 1000 densitometer. Sixty-two children with JCA and 157 healthy children, aged 5-18 years, were studied. Bone mass was measured in the lumbar spine at the L1-L4 level (LS), in the femoral neck (FN) and in the distal one-tenth radius (DR). RESULTS A decrease in bone mineral density was observed in 50-60% of the JCA patients in the three regions studied. Those patients who had undergone corticosteroid treatment showed significant bone loss in the DR and LS (trabecular bone), but not in the FN (cortical bone). Bone mass loss was seen for all three disease subtypes, being higher in the patients with polyarticular JCA (particularly in the DR), although this different was not significant. There was a significant difference in disease duration between the children with decreased BMD and those with no BMD decrease in the same regions. CONCLUSIONS A decrease in bone mineral density was found in 50-60% of all the JCA patients in this series, regardless of the disease subtype. Corticosteroid use apparently had an effect on the BMD in the trabecular bone. The data also show a correlation between the loss of BMD in both cortical and trabecular bone and a long disease duration.