EnterotoxigenicEscherichia coli, Vibrio choleraeO1,Campylobacter jejuni, Salmonellaspecies, andShigellaspecies are major causes of morbidity and death in diarrheal disease. More recently recognized pathogens areV. choleraeO139 and enterohemorrhagicE. coli. In addition to this, several presumptive virulence factors have been identified in diarrheagenicE. coliand in other species. To confirm these as virulence factors we need good diagnostic tools and good epidemiological studies. These are of vital importance to create vaccines for diarrheal diseases.