A quantitative evaluation, at the scanning electron microscopic (SEM) level, was made of the osteoconduction and osseointegration of Ti-6AI-4V implants with and without plasmasprayed hydroxyapatite coatings (HACs). By employing the Chinese Coin implant model in the lateral femora cortices of canines, different biological properties between HA-coated and uncoated Ti-6AI-4V implants could be compared in one specimen. After 4, 6 and 1 2 weeks, the implants with surrounding bone were removed and assessed histologically in undecalcified sections under SEM. The osteoconductivity and the ability of osseointegration of implants were histomorphometrically analysed from back-scattered electron images (BEIs) and represented in terms of the new bone healing index (NBHI) and apposition index (AI), respectively. Throughout all implant periods, the HA-coated Ti-6AI-4V implants revealed higher NBHI than the uncoated ones, it appearing that the HA-coated Ti-6AI-4V.implant was more osteoconductive than the Ti-6AI-4V was. For HA-coated implant, the evidence of direct bone-to-HAC contact was observed. However, at the bone/Ti-6AI-4V interface, there intervened a fibrous membrane without calcium content, indicating that the Ti-6AI-4V implant was not osseointegrated in the SEM field of view. The maximum value of AI was reached 6 weeks after implantation for HA-coated implant, implying that the HAC had a stimulating influence on bone apposition within 6 weeks of healing. The signs of partial dissolution of HACs within the remodelling canals were evident at the HAC-bone interface 1 2 weeks after implantation, accounting for the slight decrease in NBHI and the obvious decrease in AI for HAC implant.