Abstract: This paper presents the results of an electron microscopic cytochemistry study on the menbrane-bound organelles of Trichomonas hominis. Acid phosphatase (ACP) and cyti-dine monophosphatase (CMPase) were located in the primary lysosomes, digestive vacuales, as well as in the parabasal body stacks, being usually in its mature surface sacs. Thiamine pyrophosphatase (TPPase) and nicotinamide adenine dinucleotide phosphatase (NADPase) were found in the saccules, being on the mature surface and in the intermediate saccules of parabasal body stacks, respectively. The reactive products of peroxidase (POase) were seen only in the digestive vacuoles. Cytochrome oxidase (COase) and catalase (Cat) reactions were both negative. It is suggested that T. hominis lacks mitochondrion and microbody but possesses hydrogenosome. The parabasal body, endoplasmic reticulum and hydrogeno-some were stained well with the U-Pb-Cu impregnation technique. (Figsl-11)