Biphosphonates are now being used experimentally in children to increase bone mass, but their long-term effects remain an issue of concern. We report two cases of biphosphonate-induced radiographic changes in children with rheumatic diseases. Our experience supports the view that clinical improvement and radiographic findings after biphosphonate therapy are related to increased bone mineral density, without effects on the inflammatory process itself. Biphosphonates seem to act in rheumatic diseases by reducing bone turnover instead of improving disease activity.