Probiotics are a group of organism those confer health benefit to consumers. There are lots of studies about health benefits of probiotic treatments. The more commonly used probiotic bacteria are bifidobacteria and lactic acid bacteria, such as lactobacilli, lactococci and streptococci. Microorganisms that are probiotic to humans also include yeasts, bacilli and enterococci. Probiotic yeasts have become a field of interest to scientists in recent years. Several previous studies showed that members of Saccharomyces genus can possess anti-bacterial and probiotic properties. Saccharomyces boulardii is non-pathogenic yeast used for many years as a probiotic agent to prevent or treat a variety of human gastrointestinal disorders. S. boulardii is commonly used in lyophilized form especially in the pharmaceutical industry. In this review, information about the probiotics, properties of probiotic yeasts, their usage fields is provided and the results of researches in this area has been presented.