An experiment was conducted utilizing 40 male rats randomly distributed into eight groups to determine the effects of feeding four different dietary levels of solanine-containing potato upon blood composition. Two potato varieties differing in their solanine content were compared. Vitamin D was added to certain diets to compare the additive effect of solanine and vitamin D. Calcium, phosphorus, magnesium and hydroxyproline were analyzed. Serum levels of calcium, phosphorus and magnesium appeared to be somewhat decreased in the solanine-fed rats, though there was no distinguishable pattern to the percent decrease as a function of potato variety and vitamin D level. Serum hydroxyproline levels were decreased in solanine-fed rats, the percent decrease being roughly proportional to the amount of potato in the diet. Vitamin D exerted an additive effect in decreasing hydroxyproline levels. Weights. gain remained relatively unaffected by the addition of up to 30% potato in the diet. Solanine, a glycoalkaloid Found in sun-exposed potatoes, appears to exert a vitamin D-like effect in increasing calcium absorption. This is suggested by low serum hydroxyproline levels in solarine-fed rats, indicative of decreased bone resorption and increased tissue calcium concentration. Within the experimental confines of this project, it seem, reasonable to conclude that solanine exerts a more potent effect than vitamin D upon increasing calcium absorption.