In connection with the known inhibitive action of bisphosphonates on bone resorption we were interested in their possible influence on bone blood flow (BBF). We determined BBF (^Sr-microsphere uptake in the tibia, distal femur and diaphysis of femur), cardiac output, density and ash weight of the tibia, as well as 24-h incorporation of 45Ca and 3H-proline into the tibia. Pamidronate (Aredia, CIBA-Geigy, Switzerland) was administered to sham- operated or oophorectomized (OOX) female rats in doses of 0.6 mg i.p. 2 days a week for 4 weeks. ^Sr- microsphere uptake was increased after OOX in the tibia and distal femur, simultaneous pamidronate administration significantly suppressed this increase below the control level. In addition, pamidronate inhibited the 24-h incorporation of 45Ca and 3H-proline in sham-operated females and suppressed the incorporation of 3H- proline that was increased after OOX. Bone density and ash weight were significantly increased after pamidronate administration in both sham-operated and OOX rats. The results of both experiments showing a significant effect of pamidronate on BBF and incorporation of 45Ca and 3H-proline require further verification and elucidation.