With a screening hemisolid stem-cell culture, four positive hybridomas 2B(12), 2C(1), 2F(1), and 3D(4) were screened and used to prepare four correspondent monoclonal antibodies (McAbs) against the pyrethroid insecticide deltamethrin. These McAbs showed I(50) values in a range of 17-94 ng mL(-1), from among which the antibody 2B(12) with the lowest I(50) value was selected to develop an optimized enzyme-linked immunosorbent assay (ELISA). In the developed ELISA, the I(50) of deltamethrin was 17.0 +/- 3.3 ng mL(-1) and the limit of detection (LOD) was 1.2 +/- 1.3 ng mL(-1). There seemed to be little or no cross-reactivity with other tested pyrethroids and their metabolites. For validation of the assay method, environmental water samples fortified with deltamethrin were analyzed with the ELISA and gas chromatography (GC) methods. The recoveries of the developed ELISA ranged from 82 to 117%, which were close to those of the GC method (94-103%). These results suggested that the developed ELISA based on the McAb 2B(12) could be used for the rapid and sensitive determination of deltamethrin in environmental water.