The author has designed a new type of total hip prosthesis described as "madreporic" because its surface is rough and resembles some kinds of coral. This type of implant, which does not require cement, was tested on dogs. The bone-prosthesis junction was assessed using light and electron microscopy. Radio-spectrography and micro-radiography showed that osteogenesis occurred in the roughened surface of the implant leading to an early, strong and long-standing fixation. The prosthesis was inserted in two hundred patients. Five were removed after septic complications and one after premature death. The fixation with new bone to the surface of the metal was confirmed.