Emerging from the stigma of once being referred to as "snake oil", excellent scientific and clinical evidence now exists to indicate that probiotics do indeed have a role to play in medicine. The proper definition of probiotics is important "Live microorganisms which when administered in adequate amounts confer a health benefit on the host", for several reasons. It rules out so-called probiotics that have no clinically proven, peer-reviewed data, and it states the need to have viable bacteria present, unlike these pseudo products which are often wrongly labeled, poorly manufactured, with low or no viability at time of use. Guidelines, prepared by the United Nations and World Health Organization are now available to guide physicians and consumers as to the types of strains with documented benefits. In urology, the most studied strains are Lactobacillus rhamnosus GR-1 and L. fermentum B-54 and RC-14. Their use daily in oral form, or once to three times weekly as a vaginal suppository, have been shown to reduce the urogenital pathogen load and the risk of urinary tract and vaginal infections. Organisms such as Oxalobacter formigenes, still in the R&D phase, offer great potential to reduce kidney stone formation via oxalate degradation in the intestine. Some studies using L. casei Shirota suggest a possible effect against bladder cancer, while studies using L. plantarum 299 show significantly reduced infection rates in patients undergoing major surgical procedures. In short, specific probiotic strains hold much promise for use in the urology setting.