Structures of methylenedioxymethamphetamine (MDMA) and methylenedioxyamphetamine (MDA) are very similar to methamphetamine (MA) and amphetamine (AP), respectively. Immunoassay is one of useful methods detecting drugs. We have designed to prepare the antibody for recognizing MDMA and MDA. MDA was conjugated with bovine serum albumin (BSA) by glutaraldehyde method. Rabbits were immunized with MDA-BSA to obtain anti-MDA antibody and IgG fraction from the antiserum was used as an antibody. The cross-reactivity of the antibody was tested by an enzyme-linked immunosorbent assay (ELISA). MDMA showed higher reactivity to the antibody than MDA probably due to similar structures with methylenedioxy moiety. On the other hands, methamphetamine and amphetamine had low cross-reactivity to this antibody. The range of MDMA measurable by ELISA was 0.01-1 μg/well. MDMA in urine could be determined in the range of 0.2 to 20 μg/ml by ELISA using the antibody.