This study retrospectively evaluated the results of 36 sinus-lift graft augmentations performed to place 66 implant cylinders in the posterior maxilla where vertical bone height was less than ideal. Grafts were accomplished with porous hydroxyapatite (HA) alone, porous HA mixed with autogenous bone removed from the iliac crest, and HA combined with autogenous bone removed from within the mouth. Nineteen core biopsy specimens were taken from different grafts at time intervals ranging from 4 to 36 months from the time of grafting. These cores were evaluated using histomorphometric analysis to yield data comparing volume fractions of bone formation, allowing comparison of different graft materials and healing times. Grafts using porous HA alone on mean produced 16.38% bone by volume after 6 months. After the same healing time, grafts using HA and hip bone on mean produced 19.30% bone by volume compared with an 11.30% bone volume when using HA and bone harvested intraorally. Evaluation of cores taken at 19 and 36 months revealed greater volumes of bone formation. Recommendations based on clinical and histologic results are discussed in detail. Keywords: autogenous, histomorphometric, sinus-lift augmentation, volume fraction