The purpose of this study was to examine effects of leukotriene D4 on blood flow to the cerebrum and choroid plexus. Blood flow was measured with microspheres in anesthetized rabbits. Under control conditions, blood flow to the cerebrum was 37 +/- 4 ml. min-1.100 g-1 (mean +/- SE) and blood flow to the choroid plexus was 428 +/- 52 ml.min-1.100 g-1. Intra-atrial infusion of leukotriene D4 at 0.1 and 1.0 microgram.kg-1.min-1 did not alter blood flow to the brain or choroid plexus, but produced a 49 +/- 3% and 69 +/- 5% decrease in blood flow to the bowel. We also examined effects of intracerebroventricular administration of leukotriene D4. Intraventricular injection of 1.0 microgram of leukotriene D4 did not affect blood flow to the cerebrum or choroid plexus. In contrast, intraventricular injection of 1.0 microgram of angiotensin II produced a 42 +/- 4% decrease in blood flow to the choroid plexus. In summary, neither intravascular nor intraventricular administration of leukotriene D4 affects blood flow to the brain or choroid plexus.