Background and purpose: Blastocystis hominis is a common intestinal protozoon with worldwide distribution. The prevalence of this parasite varies between different countries. This study aimed at investigating the prevalence of Blastocystis in individuals attending health centers in Sari, Iran, 2014.

Materials and methods: We conducted a descriptive study in which 420 stool samples were obtained. Samples were examined using direct method, parasite test (formalin-ether), and Giemsa staining.

Results: The samples included 245 males and 175 females. Among the male and female patients 48 (11.4%) and 12 (2.8%) were Blastocystis positive, respectively.The overall prevalence of Blastocystis hominis was 14.3%. Significant relationships were observed between the prevalence of Blastocystis and gender, age, occupation, contact with animals, educational level, and place of residency (P<0.05). But, no significant relationship was found between the prevalence of Blastocystis with drinking water, bloating, diarrhea and weight loss.

Conclusion: Enhancing the individual and public levels of health knowledge, improving environmental health and safety of water supplies could help in reducing the rate of Blastocystis infection. Clinical investigation of human cases, identifying subtypes of parasites and further studies to determine the factors affecting the virulence of the parasite are recommended for future studies.