A new label-laccase from the fungus Coriolus hirsutus-was applied for solid-phase enzyme-linked immunosorbent assays of the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D). Two proposed assays are based on (1) competitive binding of antibody-laccase conjugate with immobilized 2,4-D-protein conjugate and 2,4-D in tested sample, and (2) competition of 2,4-D and 2,4-D-laccase conjugate for binding with immobilized antibodies. Kinetic and concentration dependencies for these reactions were studied, and the ELISAs were optimized in accordance with the data obtained. The elaborated systems permit the detection of 2,4-D in concentrations down to 10-20 ng/mL; time of the assays is 1.5-2 h. The main advantage of the laccase label, in comparison with the widely used peroxidase one, lies in the lack of hydrogen peroxide from substrate mixture, because dissolved oxygen plays the role of oxidizer.