Probiotics are "living microorganisms which upon ingestion in certain numbers exert health benefits beyond inherent general nutrition". Since 1987, when the first publication on the properties of the Lactobacillus GG was done, overall, there have been over 200 publications in peer-reviewed scientific journals. This paper will report the status and the prospectus of probiotics research at the beginning of the Third Millennium. Probiotics have proven benefits in treatment and prevention of rotavirus diarrhoea in children and reduction of antibiotic-associated intestinal side-effects. Interesting results have recently been published regarding food allergies and atopic eczema in children. Prevention of vaginitis and of travellers' diarrhoea have also been reported. Promising results are being reported in patients with inflammatory bowel disease, cystic fibrosis, dental caries and irritable bowel syndrome. It has also been suggested that probiotics could enhance oral vaccine administration, and that they may help treatment against Helicobacter pylori infection, but further studies are needed. Future areas of research regard probiotics' role in the process of carcinogenesis, given their influence on the gut microflora, and as immune modulators in autoimmune disorders. The possibility of introducing appropriate genes to the probiotics to make them produce various compounds is also under investigation. However, there is still confusion in the minds of the authorities over whether a probiotic is a drug, a food, or a dietary supplement. The challenge is to continue research to define the appropriate uses of probiotics and discover new applications which will bring benefit to humankind.