Probiotics have been defined a number of times. Presently the most common definition is that from the FAO/WHO which states that probiotics are “live microorganisms that, administered in adequate amounts, confer a health benefit on the host.” One of the most significant groups of probiotic organisms are the lactic acid bacteria, commonly used in fermented dairy products. There is an increase in interest in these species as research is beginning to reveal the many possible health benefits associated with lactic acid bacteria. The difficulty in identifying and classifying strains has complicated research, since benefits may only be relevant to particular strains. Nevertheless, lactic acid bacteria have a number of well-established and potential benefits. They can improve lactose digestion, play a role in preventing and treating diarrhea and act on the immune system, helping the body to resist and fight infection. More work needs to be done to authenticate the role lactic acid bacteria might play in antitumor effects, hyper cholesterol effects, preventing urogenital infections, alleviating constipation and treating food allergy.