Abstract: 　Objective To observe the morphology and ultrastructure of Blastocystis hominis. Methods Morphological observation was made with 4-5 days cultured B.hominis by light microscopy, and similar material fixed with 4% glutaraldehyde was used for transmission electron microscopy. Results Several forms of B.hominis were observed including vacuolar, \{granular\}, amebic, multifission and cystic forms. The multiplication patterns of B.hominis included both binary fission and sporogony. Under transmission electron microscope, the nuclei, mitochondria, rough endoplasmic reticula and lysomes were observed in addition to lipid droplets in its cytoplasm, and glycogen in the central vacuole. Conclusion The central vacuole of vacuolar form may be related to the storage of the excreta. The amebic form of B.hominis might be pathogenic.

Key words: Blastocystis hominis, morphology, ultrastructure