Ultrastructure of the hemocytes in Lymantria dispar L. was studied using transmission and scanning electron microscopes. The 4 types of hemocytes were identified in the larval stage. Prohemocyte was small size which Nucleus was eccentric, and electron density of its cytoplasm was relatively high. Plasmatocyte were ovoid or elongated cells in which cell organeles well developed, this cell micropapilla. Granulocytes contained numerous granules which were identified 3 types ($circled1$ structureless, electron-dense granules, $circled2$ structureless, thinly granules, and $circled3$ structure granules.). Spherulocytes as the large cells in which cytoplasm was compacted with spherules which contained filamentous material. The electron density of spherules appeared constant.