Blastocystosis is a protozoan disease of the small intestine, caused by various subtypes of Blastocystis sp. The absence of studies regarding disease prevalence in stray dogs in Greece (in particular in the greater Komotini area) and the potential effects on Public Health was the basic incentive for this study. The study is separated in two sections. In the first one, a review of Blastocystosis is presented. Blastocystis is considered one of the most common protozoans isolated from faecal samples of humans. Blastocystis has also been isolated from a wide spectrum of hosts, including mammals, birds, amphibians, reptiles and insects. In Greece, Blastocystis sp. has been detected in pig, sheep, bear, chicken, ostrich and humans. In humans, it constitutes a frequent finding of faecal samples obtained from immunosuppressed individuals with or without symptoms. The parasite can be presented with the following forms: vacuolated, non vacuolated, granular, entamoebic and cystic, both in humans and animals. Man and other hosts become infected by the ingestion of the vacuolated form of the parasite when consume food or water contaminated with infected faecal material. Blastocystis sp. is considered the causative agent for certain diseases of the small intestine. However, the exact role of the protozoan in the pathogenesis of the disease has not been fully clarified yet. Blastocystosis is usually asymptomatic, although 50% of the infected or immunosuppressed individuals present gastrointestinal symptoms of varying severity. The diagnosis is based on the detection (or isolation) of the parasite in faecal samples. In the second section, the research protocol applied in study is presented including animals examined, materials and methods, results and discussion. 27 faecal samples obtained from stray dogs in the greater Komotini area were examined by a specific PCR for the detection of Blastocystis sp. All samples were negative for Blastocystis sp. These preliminary results indicate that the absence of Blastocystis infection in stray dogs poses no risk for Public Health, since the disease has been confirmed to be a zoonosis. However, a large scale 39 research is needed to be carried out in Greece in order this preliminary assumption to be confirmed.