The objective of this program is the evaluation of the long term behavior of endosteal porous metal dental implants used in full function as tooth replacements in macaque nemestrina monkeys. Prosthesis stability is achieved by bone ingrowth into the Void-Metal-Composite (VMC) implant, a porous titanium alloy base material. Gold crown restorations attached to the VMC implants allow the prosthesis to be evaluated under the stresses of full occlusal function. The VMC implants are of cylindrical shape, and made of Ti-6A1-4V alloy with interconnecting pores of 450micron diameter. We are currently proposing a continuation of our existing grant into the fifth program year. A total of 18 animals, carrying 78 implants, 68 of which are crowned, are involved in the studies. Implant times range from 1/2 to 3 years, as of 2-79. The performance of the implants to date is highly encouraging, with an observed failure rate of less than 10 percent. The planned activities for the fifth program year include sacrifice of three animals, one of which will have an accrued implant time of 4 years.