The chondrogenic potential of free autogenous periosteal grafts for osteochondral defects was investigated at the Department of Orthopaedic Surgery, Yonsei University, Wonju College of Medicine. Five millimeter diameter of circular full-thickness defects were made in patellar groove of both femur in 64 adolescent rabbits and the rectangular periostei, prepared from the proximal tibiae, were placed over the defects of patellar groove and sutured(cambium layer, facing joint surface) and the rabbits were allowed to move actively. A serial gross and histologic examinations of neochondrogenesis were done during 8 weeks. The results were as follows. l. At 2 weeks after operation, neochondrogenesis was hardly seen either in the graft group or in the control group. The defects were partially filled with some fibrous tissue. 2. After 6 weeks of operation, all defects in the graft group(postop 6 weeks and 8 weeks) were filled with hyaline cartilage cells but only 38% (postop 6 weeks) and 44% (postop 8 weeks) of the control group were filled with hyaline cartilage cells. 3. The cartilages, formed at 6 and 8 weeks, were more mature and better than those formed at 4 weeks. 4. The newly formed hyaline cartilage of the graft group filled the defect earlier and were better than those of the control group. 5. The chondrocytes in the newly formed tissue were originated from the cambium layer of periosteal grafts. 6. Free autogenous periosteal grafts can repair a full-thickness defect in a joint surface by producing tissue that resembles articular cartilage grossly and histologically.