The aim of the study was to develop a sensitive and specific ELISA for the detection of LT enterotoxin in E. coli strains. The test was based on the antitoxic antibodies obtained from rabbits immunized with В subunit of cholera toxin (CT). The toxin was structurally closely related with LTB of E. coli. CTB was expressed in a V. cholerae strain harboring a plasmid with a ctxB gene. The toxin was isolated and purified from a growth medium by means of precipitation. A goat antirabbit IgG labeled with HRP antibodies was used as a conjugate. The developed test turned out to be highly specific and sensitive: it was possible to detect from 1.5 to 4.0 ng of LTB. One hundred strains of E. coli isolated from piglets were tested by the LT ELISA. It was found that 67 strains (85.9%) isolated from piglets with diarrhea were LT+ whereas only 2 strains (9.1%) from healthy piglets proved to be enterotoxigenic.