Abstract: The surface structure of Clonorchis sinensis cercariae was observed under scanning electron microscope.The cercaria was of the parapleuro-lophocercous type. The measurements of the cercariae were as follows: body 137-240 × 62-90μm, tail 320-470 × 21-34μm, oral sucker 27-46 × 23-33μm. The ventral sucker was incompletely developed and much smaller than the oral one. The whole body surface was covered with backward pointing spines. Four horizontal rows of oral spines were found around the mouth opening of the oral sucker. These spines diminished in size with the distance of the rows from the opening and their numbers were 12,18, 19 and 18 respectively. Transverse and longitudinal plicae formed from tegument were found on the surface of the tail, being in connection with dorsal and ventral fins along posterior half of the tail. Many sensory structures or papillae were observed on the body. They were of three different types: 1) papillae with long or short cilia distributed widely on the body surface and around the mouth opening, the number of papillae with cilia on the body surface being greater than that described by Komiya et al(1940); 2) a few sensory fossa on the tail, measuring 1.0×0.6μm; 3) a few ring-type papillae with knob on the body surface with pore of 0.5μm in diameter (FigS, 1-8).