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An ELISA method on microtitration plates to detect and assay Escherichia coli heat-labile enterotoxin (LT) is described. This technique is rapid and simple to perform in any laboratory. It allows detection of the presence of LT with the naked eye within 10 h in a 12-h E. coli culture supernatant. The reaction is based on immunological cross-reaction between LT and the Vibrio cholerae toxin (CT). In place of traditional microtitration plates coated with ganglioside Gm1, we propose a new polystyrene support coated with purified anti-CT antibodies. This coated support has been conditioned in a kit to be used in laboratories in bush dispensaries of endemic areas. It was tested with 40 enterotoxigenic (LT+) strains isolated from stools of diarrhoeal children and with 14 LT- strains. All supernatants LT+ and LT- were found positive and negative, respectively, with the ELISA method and with the new polystyrene support. Field tests (in Wallis, Futuna et Vanuatu) with the new kit and standard method were satisfactory.