Young rabbits on high (0.57%) or low (0.24%) calcium were given an aqueous extract of Solanum malacoxylon (S.m.) leaves (20 g dried leaves/200 ml distilled water) intragastrically at 0, 12 and 36 hours. On bothe diets S.m. induced progressive hypophosphatasemia but serum calcium and phosphorus underwent only minor changes. In rabbits necropsied at 0, 12, 36, 60, 84 and 108 hours, S.m. was shown to have a negative effect on the resorbing osteocytes. With retarded osteocytic osteolysis, osteopetrosis resulted. Further regressive changes in the osteocytes resulted in osteonecrosis which was observed within 12 hours after administration of S.m. extract. The osteonecrosis, combined with retarded apposition, later resulted in osteopenia. It was concluded that the recommended dietary calcium for growing rabbits--about 0.6%--is too high. Whereas the histologic appearance of bone in rabbits fed low calcium was normal, bones from rabbits on high calcium showed retarded resorption and the rabbits had a relative hypophosphatasemia.