A dividable titanium implant was inserted in the tibial metaphysis of rabbits, which permitted a numerical evaluation of ingrowing bone. The implant on the test side was used as cathode and was connected to a subcutaneously located stimulator delivering constant current of either 5 microA, 20 microA, or 50 microA. A corresponding control implant was inserted in the other tibia of the same animal and treated likewise, but was not connected to the stimulator. Distally to each implant, a platinum-iridium screw was inserted into the cortex and connected on the test side to the stimulator to serve as the anode. The results showed a 2.4-fold increase in bone formation with 5 microA. In the 20-microA group, there was 2.6-fold more bone in the test chambers. Direct current (DC) stimulation with 50 microA caused a clear decrease of bone volume, with an average of 48% less bone in the test implants. The results indicate that 5 and 20 microA direct current enhance bone ingrowth into a titanium implant that is used as a cathode. The osteogenesis seemed to be more pronounced in the case where the chamber was used as a cathode compared to earlier experiments in which the cathode was placed at a distance of 5 mm from the implant.