Objective:To determine the expression and localization of tartrate-resistant acid phosphatase (TRAP) in different cells of skeletal tissue. Methods: The activity and protein localization of TRAP in different cells of skeletal tissue of tibiae from 6-week-old C57BL/6J mice were examined by histochemistry,immunohistochemistry or histochemical and immunohistochemical double staining. Results: Strong positive reaction for TRAP was detected in osteoclasts and positive reaction was also detected in chondrocytes from articular cartilage and growth plates,osteoblasts and periosteal cells by both histochemistry and immunohistochemistry. Histochemical and immunohistochemical double staining demonstrated that the most of TRAP immunopositive cells also showed histochemical positive reaction for TRAP,but some TRAP immunopositive cells were histochemical negative for TRAP. Conclusion: The TRAP not only highly express in osteoclasts,but also express chondrocytes of articular cartilage and growth plates,osteoblasts and periosteal cells.