Osseointegration refers to a direct structural and functional connection between ordered, living bone and the surface of a load-carrying implant. Currently, an implant is considered as osseointegrated when there is no progressive relative movement between the implant and the bone with which it has direct contact. A direct bone contact as observed histologically may be indicative of the lack of a local or systemic biological response to that surface. It is therefore proposed that osseointegration is not the result of an advantageous biological tissue response but rather the lack of a negative tissue response. The rationale of the present review is to evaluate the basic science work performed on the concept of biology of osseointegration, and to discuss the specific factors as they may relate to osseous healing around an implant.