Probiotics are live microbial food supplements or their components, which have been shown to have beneficial effects on human health. Probiotics can be bacteria, molds, or yeasts, but most of them fall into the group known as lactic acid bacteria and are normally consumed in the form of yogurt, fermented milk, or other fermented foods. Data from clinical trials have shown contrasting effects and should be interpreted with caution. A large variety of potential beneficial effects have been reported including improvement of intestinal tract health, enhancing the immune system, reducing symptoms of lactose intolerance, decreasing the prevalence of allergy in susceptible individuals, reducing risk of certain cancers, treating colitis, lowering serum cholesterol concentrations, reducing blood pressure in hypertensives, and improving female urogenital infections and Helicobacter pylori infections. The aim of this article is to present a review of the current expanding knowledge of applications of utilizing probiotic microorganisms in the prevention and treatment of several diseases.