Many bacterial species are responsible for sporadic cases and outbreaks of foodborne intoxication and infection. The foodborne diseases are classified on the basis of the pathogenetic mechanisms involved into four categories: performed toxin, enterotoxin formed in the colonized small intestine, mucosal invasion (enterocolitis) and mucosal invasion with bacteremia. Invasive and toxigenic strains of enteropathogenic Escherichia coli are discussed. In vivo test systems for the identification of enterotoxigenic organisms and tissue culture assays for the heat-labile enterotoxin of E. coli are described. Current laboratory methods for the diagnosis of foodborne diseases of major public health interest are reviewed - botulism, staphylococcal intoxication, Clostridium perfringens enteritis, salmonellosis, enteropathogenic E. coli infection, Vibrio parahaemolyticus infection and Bacillus cereus enteritis. The role of the laboratory in the epidemiologic surveillance and investigation of foodborne diseases is emphasized.