The purpose of the present study was to determine the pattern of microcirculatory disturbance to investigate the causes of gastric mucosal blood flow depression in the early period after thermal injury. Male Wistar rats were anesthetized and a 30% full skin-thickness dorsal burn was inflicted. Active oxygen species (AOS) generated by circulating leukocytes were measured by chemiluminescence. Contraction of arterioles and venules was observed by intravital microscopy, and rolling or sticking of leukocytes in venules was counted using fluorescence microscopy. AOS generation by circulating leukocytes was diminished and arteriolar contraction and increases in rolling or sticking leukocytes in venules were observed 15 min after thermal injury. Decreased AOS generation by circulating leukocytes, contractions of arterioles, and increased rolling or sticking of leukocytes in venules was observed in the early period after thermal injury. Arteriolar contraction may explain decreases in mucosal blood flow. Moreover, decreased AOS generation by circulating leukocytes does not obviate the potential participation of leukocytes in microcirculatory disturbances, because rolling or sticking leukocytes were increased significantly 15 min after thermal injury.