The localization and distribution of ATPase activity in the femurs of young mice was evaluated using the lead‐ATPase histochemical method. The skeletal system demonstrated an intracellular distribution of ATPase activity. Enzyme activity of osteoclasts, and metaphyseal and perichondrial osteoblasts was high. Endosteal and periosteal osteoblasts varied in activity depending upon the area under observation. Preosteoblasts (progenitive cells) of the osteogenic periosteum, osteochondrogenic cells of the perichondrial region, chondrocytes, and cells of the fibrous periosteum demonstrated minimal activity. Osteocytes were negative. The distribution of osteoblast APTase activity coincided with areas of active collagen synthesis.