The author studied the effects of some dental gold alloys and dental nonprecious metals on muscle. The metal specimens were cast in the size of $1.0mm.{ imes}5.0mm.{ imes}3.0mm.$ and implanted in the gluteus maximus musculus of the two dogs. The subjects were sacrificed at 3 weeks and 5 weeks respectively after implantation. The tissue was examined his to-pathologically. The findings were as follows. 1. The more the alloy contains gold, the less the tissue response to the alloy and the less the connective tissue layer around the specimens. 2. The recovery of connective tissue layer in gold specimens was markedly observed. 3. There were very thick connective layers around nonprecious specimens.