This experiment evaluated the influence of blood on the weld strength of laser-assisted microvascular anastomoses (LAMA). Rat femoral arteries were anastomosed end-to-end by either direct laser welding (group I) or by a blood-bonded technique (group II) whereby fresh blood was applied to the vessel edges before laser exposure. Bursting strength was measured at 0, 1, and 24 hours and at 3 and 7 days by infusing methylene blue into the vessel while pressure was monitored. The results showed significantly increased bursting strength in group II compared with group I at 0 hour and 7 days (P less than 0.05). There was a significant increase in bursting strength in group I from 0 hour to 1 hour (P less than 0.05). It is concluded that blood-bonding enhances the early bursting strength of LAMAs and may facilitate arterial wall healing.