Seven patients with severe neuromuscular symptoms due to hypomagnesaemia together with hypocalcaemia following extensive resection of the small bowel were treated orally with 1 alpha-hydroxylated metabolites of vitamin D and magnesium oxide. There was a rapid response in both plasma calcium and magnesium concentrations. The mean plasma magnesium rose from 0.24 to 0.45 mmol/l with the vitamin D metabolites alone and to 0.81 mmol/l when magnesium oxide was added. The plasma calcium rose from 1.78 to 2.21 mmol/l on vitamin D alone and then remained within the normal range. This was accompanied by a rapid resolution of the neuromuscular symptoms. Such oral treatment is both acceptable to the patient and effective both for acute symptoms and in the long term to maintain plasma magnesium concentrations.