There is in 1993 no proven medical indication of lactic acid bacteria (LAB) for therapy or immunomodulation in man. However, within the bulk of publications, rigorous trials have now opened rational fields of research on beneficial effects of LAB. These include lactose digestion, cholesterol metabolism, diarrheal disorders, prophylaxis of intestinal or urogenital infections, immunomodulation or even oral vaccination. We try here to analyse these studies, considering LAB as pharmacological agents, and conclude that pursuit of research could be promising for ecological therapy of mucosal diseases, and for development of original and flexible vectors for targeting in the gastrointestinal tract.