One hundred and eighty-six cases of milk fever in 80 herds spread over five counties were used to compare treatment with 8g calcium plus 500 mg magnesium in aspartate with the conventional 12-36g calcium as borogluconate. The data obtained from both the herds and their individual cases show that the treatments gave broadly similar results, and a single intravenous treatment cured 74-7 per cent of cases. It appeared that milk fever was not likely to recur with each succeeding parturition. No breed susceptibility was recognised. No correlation was found between the severity of the clinical signs and the inorganic phosphate concentrations. An incidence of milk fever of 8-79 per cent was recorded.