&NA;Blood flow in sinus grafts and adjacent oral tissues was investigated using Laser Doppler Flowmetry (LDF). Special LDF probes were inserted into pilot drill holes before the final sizing drill to prepare recipient dental implant sites in the grafted sinus after a 6‐month maturation time. Patients in the study had previously undergone sinus grafting with irradiated mineralized cancellous allografts alone, which had been prepared by either hydration in saline or autogenous serum. LDF detected positive blood flow in all sites investigated. No significant differences were recorded between saline‐ and serumtreated grafts. However, blood flow at the superior aspect of the grafts was significantly lower than that recorded at midway and at the most inferior aspects of the sinus grafts. Sinus membrane blood flow was noted to be very low compared with bone and mucosal sites. LDF may be a useful technique in the verification of vitality in sinus grafts relative to that of adjacent oral structures. (Implant Dent 2000;9:133‐142)