Osteoporosis is one of the most difficult problems in the management of Chronic Juvenile Arthritis (JCA). The available data suggest that bone loss results from multifactorial processes which lead to bone degradation through the activation of osteoclasts. Biphosphonates are synthetic factors that, once localized on the surface of hydroxyapatite crystals, do not allow either the production or destruction of the crystals. This activity seems to be due to cytotoxicity against osteoclasts and to inhibition of prostaglandin E2 synthesis. There is some evidence that these drugs are effective in the treatment of osteoporosis in several diseases. In an attempt to reduce or prevent osteoporosis in children affected by JCA we started a trial with disodium clodronate, a type of biphosphonate. Thirteen patients were enrolled in the study: 7 received disodium clodronate and 6 acted as control subjects. Before starting the therapy and after one year we performed a CT scan to evaluate the mineral bone density in all patients. The mean bone density increased from a bone mineral content of 129 mg/cc before treatment to 134 mg/cc after treatment (8% increase); control patients passed from 123 mg/cc to 115 mg/cc (7% decrease) in the same period. Only one child stopped treatment because of gastrointestinal side effects. The small number of patients enrolled in the trial does not allow any definite conclusions to be drawn, but the data are interesting and worthy of further study.