Technical Abstract: The study results of longan fruit pericarp structure cv. Daw and Biew Kiew were assessed using stereo microscopy, light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that on the surface of longan pericarp were many natural openings and cracking of the cuticle. The thin discontinuous cuticle covered the surface, some trichomes and a few stomata were scattered on the percarp surface. The transverse section was observed by SEM. Pericarp thickness was about 500-700 µm, of similar structure for both cultivars and consisted of three layers. The layers differed by cell shape and arrangement. The exocarp consisted of thin cuticle, under which there were to two to three layers of small rectangular cells in the subepidermis. The mesocarp thickness was about 70% of the total pericarp. Cells of various sizes and shapes, round and elliptical, were observed along with large intercellular spaces, vascular tissue and some stone cells. Observation by TEM found mitochondria and cell organelles within the cells in the mesocarp. However, the stone cells were surrounded by was thick secondary cell walls. The endocarp was made up of a square shaped of single cell layer. In addition, the inner side was lightly curved when assessed by SEM. The longan arils are translucent with white color in cv Daw, opaque white in cv Biew Kiew and pinkish white in cv Sri-Chomphu. The red pigment is an anthocyanin,present about one quarter of the way through thearil.