AIM:To provide scientific evidence for prevention andcontrolling of blastocystosis,the infection of Blastocystishomonis and to study its clinical significance in Huainan City,Anhui Province,China.METHODS:Blastocystis homonis in fresh stools taken from100 infants,100 pupils,100 middle school students and403 patients with diarrhea was smeared and detected withmethod of iodine staining and hematoxylin staining.Afterpreliminary direct microscopy,the shape and size ofBlastocystis homonis were observed with high power lens.The cellular immune function of the patients withblastocystosis was detected with biotin-streptavidin(BSA).RESULTS:The positive rates of Blastocystis homonis infresh stools taken from the infants,pupils,middle schoolstudents and the patients with diarrhea,were 1.0%(1/100),1.0%(1/100),0%(0/100)and 5.96%(24/403)respectively.Furthermore,the positive rates of Blastocystishomonis in the stool samples taken from the patients withmild diarrhea,intermediate diarrhea,severe diarrhea andobstinate diarrhea were 6.03%(14/232),2.25%(2/89),0%(0/17)and 12.31%(8/65)respectively.The positiverates of Blastocystis homonis in fresh stools of male andfemale patients with diarrhea were 7.52%(17/226)and3.95%(7/177)respectively,and those of patients in urbanand rural areas were 4.56%(11/241)and 8.02%(13/162)respectively.There was no significant difference betweenthem(P>0.05).The positive rates of CD_3~+,CD_4~+,CD_8~+ inserum of Blastocystis homonis-positive and-negativeindividuals were 0.64±0.06,0.44±0.06,0.28±0.04 and0.60±0.05,0.40±0.05 and 0.30±0.05 respectively,andthe ratio of CD_4~+/CD_8~+ of the two groups were 1.53±0.34and 1.27±0.22.There was significant difference betweenthe two groups(P<0.05,P<0.01).CONCLUSION: The prevalence of Blastocystis hominis as an enteric pathogen in human seems not to be associated with gender and living environment, and that Blastocystis hominiss more common in stool samples of the patients with diarrhea, especially with chronic diarrhea or obstinate diarrhea. When patients with diarrhea infected by Blastocystis hominis, their cellular immune function decreases, which make it more difficult to be cured. AIM: To provide scientific evidence for prevention and control of blastocystosis, the infection of Blastocystishomonis and to study in clinical significance in Huainan City, Anhui Province, China. METHODS: Blastocystis homonis in fresh stools taken from 100 infants, 100 pupils, 100 middle school students and 403 patients with diarrhea was smeared and detected with method of iodine staining and hematoxylin staining. The shape and size of Blastocystis homonis were observed with high power lens. The cellular immune function of the patients with blastocystosis was detected with biotin-streptavidin (BSA). RESULTS: The positive rates of Blastocystis homonis infresh stools were taken from the infants, pupils, middle school students and the patients with diarrhea, were 1.0% (1/100), 1.0% (1/100), 0% (0/100) and 5.96% (24/403) respectively. Frthermore, the positive rates of Blastocystishomonis in the stool samples taken from the patients with milk diarrhea, intermediate diarrhea, severe diarrhe a andobstinate diarrhea were 6.03% (14/232), 2.25% (2/89), 0% (0/17) and 12.31% (8/65) respectively.The positiverates of Blastocystis homonis in fresh stools of male andfemale patients with diarrhea were 7.52% (17/226) and 3.95% (7/177) respectively, and those of patients in urban and rural areas were 4.56% (11/241) and 8.02% (13/162) respectively. There was no significant difference betweenthem (P> 0.05) .The positive rates of CD_3 ~ +, CD_4 ~ +, CD_8 ~ + inserum of Blastocystis homonis-positive and -negativeindividuals were 0.64 ± 0.06,0.44 ± 0.06,0.28 ± 0.04 and0.60 ± 0.05, 0.40 ± 0.05 and 0.30 ± 0.05 respectively, and the ratio of CD_4 ~ + / CD_8 ~ + of the two groups were 1.53 ± 0.34 and 1.27 ± 0.22.There was significant difference betweenthe two groups (P <0.05, P <0.01) .CONCLUSION : The prevalence of Blastocystis hominis as an enteric pathogen in human seems not to be associated with gender and living environment, and that Blastocystis hominis s more common in stool samples of the patients with diarrhea, especially with chronic dia rrhea or obstinate diarrhea. When patients with diarrhea infected by Blastocystis hominis, their cellular immune function decreases, which make it more difficult to be cured.