The aim of the study was to evaluate whether in diabetics with good metabolic control and without any diabetic complications, disturbances of calcium, phosphorus and magnesium metabolism or hormonal regulation (parathormone/calcitonin) were present, and if they depended on type of diabetes, duration time of diabetes, kind of hypoglycaemic treatment, sex or age of patients. 83 subjects were examined, including: 14 with type 1 diabetes mellitus, 49 with type 2 diabetes mellitus and 20 healthy persons. All tests were performed in standarized low-calcium diet conditions. In basal conditions both serum concentrations and daily urine excretion of calcium, phosphorus, magnesium were estimated. Oral and intravenous calcium load tests with simultaneous parathormone, calcitonin, calcium, magnesium and phosphorus concentrations estimation were done. The final conclusions were as follow: Both in type 1 diabetes mellitus and type 2 diabetes mellitus subjects with good metabolic compensation and without advanced diabetic complications a tendency to early disturbances of calcium-phosphorus metabolism is observed. Physiological hormonal control (parathormone/calcitonin) is preserved. Correlations between mineral metabolism and type of diabetes, duration time of diabetes, daily insulin dose, body mass index and sex are observed. Kind of hypoglycaemic treatment has only slight influence on the mineral metabolism.