Strains of enterotoxigenic Escherichia coli (ETEC) are responsible for significant rates of morbidity and mortality among children, particularly in developing countries. The majority of clinical and public health laboratories are capable of isolating and identifying Salmonella, Shigella, Campylobacter, and Escherichia coli O157:H7 from stool samples, but ETEC cannot be identified by routine methods. The method most often used to identify ETEC is polymerase chain reaction for heat-stable and heat-labile enterotoxin genes, and subsequent serotyping, but most clinical and public health laboratories do not have the capacity or resources to perform these tests. In this study, polyclonal rabbit and monoclonal mouse IgG2b antibodies against ETEC heat-labile toxin-I (LT) were characterized and the potential applicability of a capture assay was analyzed. IgG-enriched fractions from rabbit polyclonal and the IgG2b monoclonal antibodies recognized LT in a conformational shape and they were excellent tools for detection of LT-producing strains. These findings indicate that the capture immunoassay could be used as a diagnostic assay of ETEC LT-producing strains in routine diagnosis and in epidemiological studies of diarrhea in developing countries as enzyme linked immunosorbent assay techniques remain as effective and economical choice for the detection of specific pathogen antigens in cultures. Key words: detection -antibodies -heat-labile toxin -Escherichia coliDiarrhea caused approximately two million deaths per year worldwide in the last decade (WHO-UNICEF 2002), and was responsible for an estimated 16-32% (median 21%) of mortality in children aged 0-4 years in developing countries (Kosek et al. 2003). One of the major etiologic agents is enterotoxigenic Escherichia coli (ETEC), known to be endemic in essentially all developing countries. Besides ETEC strains are also usually responsible for the acute diarrhea that affects visitors to the tropics (Ericsson 2003). In Brazil, these pathogens are responsible for up to 20% of cases of infantile diarrhea, region and season dependent (Reis et al. 1982, Trabulsi et al. 1985, Gomes et al. 1991, Almeida et al. 1998, Souza et al. 2002, Fernandes-Filho et al. 2003, Franzolin et al. 2005, Barreto et al. 2006 erogeneous family of lactose-fermenting E. coli, belonging to a wide variety of O antigenic types. These strains produce enterotoxins (heat labile and/or heat stable), and colonization factors, which allow the organisms to readily colonize the small intestine and in this way cause diarrhea (Sack 1980, Wolf 1997, Nataro & Kaper 1998.Since ETEC can be recognized by the enterotoxins it produces, diagnosis must depend upon identifying either heat-labile toxins (LT) and/or heat-stable toxin (ST). One or both toxins may be expressed by ETEC. LT belongs to a structurally and functionally related AB 5 enterotoxin family, in which the A subunit has the toxic activity and B subunit is responsible for toxin binding to cell receptor.Enzyme-linked immunosorbent assay (ELISA) techniques emplo...