The present study was carried out on a total of 200 patients presenting with different colonic diseases and 50 individuals as a control group, to detect the prevalence of Blastocystis hominis among patient with different colonic manifestations (IBS, ulcerative colitis, hemorrhoids, anal fissure, colonic adenoma and cancer colon). All stool samples were subjected to: a) copro-paraitological examination using direct wet smear, formol ether concentration technique and staining with three different stains (Giemsa, Modified trichrome. Acid fast trichrome) b) culturing in jones̕ media c) examination of the size and morphological details of detected parasite using micrometry and Transmission electron microscope.Considering the culture as the gold standard test, sensitivity of stool microscopy using the direct examination and concentration technique and that of stool microscopy using three permanent stains was found to be 70.5%, 61.2% and 75.2% respectively with a statistically significant difference. And regarding the prevalence of Blastocystis hominis among different colonic diseases it was found that colo-rectal carcinoma recorded the heighst percentage of infection (51%) followed by irritable bowel syndrome patients (45.6%), then ulcerative colitis patients (38.4%) while colonic adenoma showed the least percentage of infection with B.hominis (25%).