The objective of this study was to investigate the effects of inositol and vitamin D2 on bone uptake of 45Ca in rats. The radioactive calcium was administered to young rats by orogastric intubation (2 muci/100 g body weight (b. wt)) with inositol (20 mg/100 g b. wt.) and/or vitamin D2 (5OO IU/100 g b. wt.) to normal rats. Bone uptake of 45Ca was measured after 24 hours by standard technique. Inositol alone produced a 48% increase in calcium uptake. It is concluded that inositol significantly increases bone uptake of radioactive calcium (P greater than 0.005). Simultaneous administration of vitamin D2 decreases the effect of inositol considerably, while vitamin D2 has no significant effect.