Bone matrix gelatin, prepared by sequential chemical treatment including decalcification with 0.6 N hydrochloric acid [9], was used as an alloimplant for the treatment of benign bone tumours, tumorous conditions of bone, acetabular dysplasia, delayed union, traumatic bone defects and other disorders. The bone matrix gelatin implanted into bone defects was incorporated successfully in 98% of implantations, excluding cases of infection, tumour recurrence and recurrence of tumorous conditions. The material was also implanted into ten bone sites as an onlay but in five it was resorbed without new bone formation. The incorporation of the bone matrix gelatin into the recipient bed was completed from 6 to 33 months (average 14.9 months) after implantation. Wound infection complicated 5 of 165 implantations (3%) in previously uninfected sites. Low grade fever persisting after the tenth post-operative day (a probable sign of immunological reaction) occurred in 4 of 160 implantations (2.5%), excluding cases of infection. Alloimplants of bone matrix gelatin are thus effective in the treatment of bone defects. The risk of complication such as rejection or infection is low.