Abstract: This paper gives detailed description of the fine structure of Balantidium ctenopharyngodoni Chen, 1955 with an emphasis on its somatic cortex. The components of the somatic pellicle and infraciliature are described herein, especially the microtubules layer and kinetosome-associated fibrils (kinetodesmal fibril, postciliary microtubules, transverse microtubules T1, T2 and nematodesmata). Besides, the ecto-endoplasmic boundary microfibrillar layer as well as the layer of enigmatic electron-transparent vacuoles beneath this layer within the endoplasm were studied and their possible functions were discussed.