This study was designed to examine the sequential progress of healing, at two different time intervals, following delayed sinus augmentation using bovine hydroxyapatite (BHA) as the sole grafting material. Fourteen pairs of bone biopsies were taken from 10 patients after 6 and 12 months of healing, respectively. The biopsy specimens were examined histologically and histomorphometrically. The bone that was formed following sinus augmentation with BHA increased and matured over time up to 12 months after grafting; meanwhile, no overt signs of resorption of BHA were visible within the study period.