The role of probiotics in treating or preventing diarrheal diseases is well known. Less understood is the impact probiotics may have on maintaining health. Although it can be a challenge to demonstrate improved health of an already healthy population, some recent studies provide evidence that probiotics may reduce the risk of getting sick in populations that are at risk by nature of environmental exposure (eg, children in day care centers), physical status (eg, premature infants or people taking antibiotics), or family history of disease (eg, infants with a primary relative with atopic disease). These benefits may be the result of improved immune status, fewer intestinal infections, or improved intestinal integrity. The live microorganisms mediating these effects may be delivered in different formats, but the role of yogurt as a delivery vehicle for efficacious probiotics is specifically discussed.