This study sought to clarify the effectiveness of bFGF-gelatin hydrogel complex on bone regeneration around implants for the development of a new drug delivery system for bone augmentation. Twenty-four titanium implants (03.3 mmX 10 mm) were placed into edentulous areas of the mandibles of four beagle dogs with the upper four screw threads exposed at buccal side. bFGF-gelatin hydrogel complex with 0, 0.1, 1, 10, 100 microg bFGF or autogenous bone (as control) then filled the bone defect site to cover the exposed screw threads. After eight weeks, tissue specimens including implants were evaluated histologically and histomorphometrically. Histological observation showed new bone formation around exposed screw threads in the groups with 1, 10, 100 microg bFGF and autogenous bone-a striking contrast to the groups with contents of 0 and 0.1 microg bFGF. These results thus suggested that bFGF-gelatin hydrogel complex using an optimum amount of bFGF was useful for bone augmentation around implants.