Background: It is not clear whether Blastocystis hominis simply resides in the digestive tract without causing harm or it plays an important role in immunocompromised persons. Aim of the work: Is to determine the frequency of B. hominis infection among immunocompetent and immunocompromised children and to correlate some sociodemographic, hygienic and symptomatic factors with B. hominis infection. Methods: 101 children were enrolled in this study. They are categorized into 2 groups immunocompromised leukemic cases and immunocompetent (controls). Their stool specimens were examined microscopically by oil immersion lens using trichrome stain. Results: B. hominis was detected in 54.5% of immunocompromised and 67.4% of immunocompetent ones. Children aged 5
