Recently we have isolated Trichomonas hominis from diarrheic stools of a patient and established it in an axenic culture medium. The procedures are as follows: Diarrheic stool containing numerous trophozoites was first inoculated into the TYM (Trypticase Yeast extract Maltose) medium of Diamond (1975) to establish a polyxenic culture. Antibiotics, containing penicillin (1000 U/ml), streptomycin (1000 micrograms/ml), and cephalosporin (20 micrograms/ml) were added to prevent overgrowth of bacteria and fungi. After several passages, a specially-designed culture-tube was employed to separate T. hominis from the contaminants. The isolated T. hominis was then introduced into the modified TYI-S-33 (Trypticase Yeast extract Iron-Serum-33) medium of Diamond (1978). The organism established itself readily to this axenic culture medium. Sterility tests employing fluid thioglycollate, nutrient broth, and blood agar plate gave negative results indicating the absence of contaminants. The axenic culture of T. hominis provides us with a source of pure flagellates for biological, biochemical, and immunological studies.