Intestinal microbiota contribute in many different ways to our health; disturbances in the activity and/or composition of these microbiota may negatively influence health. In order to maintain a healthy intestinal microbiota, prebiotics and probiotics can be used. Selected probiotic strains safely shorten the duration of rotavirus diarrhea, relieve symptoms of lactose maldigestion and elicit beneficial immune-modulating effects. Other beneficial health effects have also been attributed to probiotics; however, these have not been sufficiently substantiated. Additional research into the mechanisms of probiotics is required.