The hemodynamic role of prostaglandins in the inflammatory phase of bone healing was studied on day 4 after creation of a nailed midtibial osteotomy in 40 rabbits, divided into groups of 10, treated with either indomethacin (oral dosage 10 mg/kg), subcutaneous (s.c.) prostaglandin E2 (PGE2) (dosage 1 mg/kg), or PGE2 infusion into the abdominal aorta (rate 20 ng/kg/min) for a 20-min period immediately before the animals were killed. The last group served as controls. Regional blood flow was measured by means of radioactive microspheres, and plasma volume was assessed by distribution of circulating [125I]fibrinogen. Neither indomethacin nor s.c. PGE2 treatment had any hemodynamic effects in the osteotomy area. PGE2 infusion caused increased blood flow in bone, bone marrow, and muscle of the lower limbs except in the osteotomy area. Thus, the influence of prostaglandins and indomethacin on bone healing of a rabbit midtibial osteotomy does not appear to be a direct vascular effect in the early healing phase.