When an acetabular cup used in hip replacement surgery is to be affixed to the acetabulum using screws, the drill guide instruments of the invention are used to position a drill bit so that the screw holes drilled in the acetabulum are properly placed for optimum implantation of the acetabular cup. The drill guide is locked into the acetabular cup by spring loaded pins which position the guide over holes in the cup which accommodate the screws. The guide is used to position the drill bits and allow drilling. After drilling the guide is removed.
