Milk of calcium developed in 2 children with juvenile dermatomyositis. The fluid of the collection contained macrophages, interleukin-6, IL-1, and tumor necrosis factor. The patient who had dystrophic calcinosis had a dramatic improvement with the introduction of alendronate. These findings suggest that calcinosis of juvenile dermatomyositis may be mediated by activated macrophages and that alendronate can be an effective treatment for this condition.