The specificity of conjugation site for coating ligands was investigated using toluene-bovine serum albumin (BSA) conjugates in which BSA was conjugated at the position of o-, m-, and ${ ho}-toluic$ acid. Toluene-BSA conjugated at ${ ho}-position$ showed a binding activity of about 89-95%, whereas, those conjugated at o- and m-position of toluene exhibited a binding activity of 5 and 11%, respectively. On the basis of the above result, coating ligands with various proteins (OVA, BSA, KLH) were compared by conjugating with $ ho-toluic$ acid, and toluene-KLH was considered as the best coating ligand for this ELISA. Indirect competitive ELISA method was developed using anti-toluene antibody and $ ho-position$ conjugated toluene-KLH. The dose-response curve constructed after kinetic and optimization studies showed a 1${ imes}$10-4 - 1${ imes}$102 mM detectable response range with 0.1 ${mu}M$ detectability. In specificity test of the antibody, the binding capabilities of aromatic compounds substituted with nitro-, alkyl-, chloro-, and hydroxyl group were larger rather than those of aromatic compounds (benzene, toluene and xylene) themselves. Also, tests with soil and water samples that had been spiked with toluene resulted in 102.7-113.7% recovery.