Sheep treated with a single dose of an extract of the dried leaves of Solanum malacoxylon (SM) at the rate of 0-2 g of leaves per kg liveweight produced a pronounced hypercalcaemia (49 per cent, P less than 0-005) after 24 h, which persisted for at least six days. The ultra-filtrable fraction of the serum calcium rose to approximately the same extent as the protein-bound calcium. This finding is consistent with osteosclerosis and parathyroid atrophy found to occur in cases of experimental SM intoxication. At the dose level given serum inorganic phosphorus was not significantly increased and packed cell volume, serum proteins and ceruloplasmin concentrations remained constant.