The Na-to-Ca ratio has been determined in femora of normal rats, untreated diabetic rats and diabetic rats treated with ascorbic acid. The determination was based on short-term activation and counting of the 24Na and 49Ca activities in the relevant photopeaks. The Na-to-Ca ratios were significantly increased in both treated and untreated diabetic animals as compared to intact controls due to increased Na contents in the diabetic rats.