We established blood flow (by means of 85Sr-microparticles) and 24 hours 99mTc-methylendiphosphonate (MDP) catchment and that of 85Sr (at different time intervals) in five portions of femur and 4 portions of tibia in rats. 1. We detected a marked differentiation in blood flow among all measured portions with the highest values in growth active distal femur metaphysis and proximal tibia metaphysis and with the lowest value in distal terminal tibia portion. 99mTc-MDP catchment is also highest in both metaphysis parts, and in the other parts it is differentiated similarly as the blood flow. 85Sr catchment in the early phase is very high in both metaphyses, but in several weeks it decreases to very low values; in the other parts the differences are small as well as the changes in the course of several weeks. 2. There is a considerable similarity in blood flow and 99mTc-MDP, in 85Sr catchment only high initial catchment in growth active metaphysis parts corresponds with blood flow. The time course of 99mTc-MDP and 85Sr catchment in the first hours after an intravenous injection is almost identical. The experiments showed great (up to 15-fold) local differences in blood flow among growth active and the other parts of femur and tibia in rats and a similar differentiation in 99mTc-MDP catchment, suggesting a certain relationship (but not quantitative dependency).