Calcium (Ca) absorption from milk, fish and vegetables in nine healthy Japanese young women was measured by the balance method by carrying out a study three times during the proliferative phase of the menstrual cycle. Each study lasted for seven days; the subjects were given a basal diet containing 200mg Ca for three days, following by the basal diet with additional milk or fish (pond smelt, sardine) or vegetables (komatsuna-green, Jew's marrow, saltwort) containing 400mg Ca for the remaining four days. During the study period, feces and urine were sampled daily, and blood was sampled on days 1, 4 and 8. The Ca content of the basal diet, milk, fish, vegetables, feces and urine was measured by atomic absorption spectrophotometry, and Ca balance was compared among milk, fish and vegetables. Ca balance during the basal diet period was negative, but turned positive during the last four days when the diets supplemented with milk, fish or vegetables were taken. Apparent Ca absorption from milk was 39.8%, that from fish 32.9% and that from vegetables 19.2%. During the entire study period, no fluctuations were observed in serum Ca, parathyroid hormone or calcitonin, but the serum 1-25 (OH)₂ cholecalciferol level was high during the period when the low calcium basal diet was taken.