Our study showed that hemodilution with modified fluid gelatin resulted in an increase in local cerebral blood flow (LCBF), but no change at all in local cerebral oxygen delivery (LCOD) in rats. Hemosome, a lecithin encapsulated hemoglobin having the oxygen-carrying capacity, was developed to improve LCOD by hemodilution. Therefore, we have hypothesized that LCBF & LCOD would be increased by hemodilution with hemosome. To test this hypothesis, adult male Sprague-Dawley rats weighing approximately 350g were used and divided into the hemodilution and the control groups. Hemosome was made from pig red blood cells and lecithin. It's mean diameter was approximately 0.3 um and hemoglobin concentration was approximately 4g/dl. Isovolemic hemodilution, which lowered the systemic hematocrit from approximately 50% to approximately 30%, was achieved by rapidly replacing blood with the same volume of hemosome. Ten min later, LCBF in 14 brain structures were measured using the 14C-iodoantipyrine technique. Our results showed that LCBF of the control group ranged from 115 +/- 11 ml/100g/min in the medulla to 260 +/- 31 ml/100g/min in the occipital cortex. LCBFs were generally higher (p < 0.05, MANOVA) by 16% in the hemodilution group than in the control group. However LCODs were generally decreased (p < 0.05, MANOVA) by 18% in the hemodilution group than in the control. In conclusion, hemodilution with hemosome indeed improves LCBF but lowers LCOD in awake rats.