p- and o-Aminomethamphetamine were synthesized as haptens to be coupled with carrier protein at the benzene ring of methamphetamine. Immunogens were prepared by the glutaraldehyde method or the MBS (N-(m-maleimidobenzoyloxy)succinimide) type cross-linking reagent method. In particular, immunization with p-aminomethamphetamine-bovine serum albumin (BSA) conjugate prepared by the glutaraldehyde method gave an anti-methamphetamine antiserum having a low cross-reactivity with methylephedrine. With the antiserum, three kinds of immunoassays for methamphetamine were established. An enzyme immunoassay (EIA) and an enzyme-linked immunosorbent assay (ELISA) were developed with alkaline phosphatase (ALP) as a label enzyme. The amount of antibody bound ALP conjugate was determined by its activity in dephosphorylating p-nitrophenyl phosphate in EIA and nicotinamide adenine dinucleotide phosphate (NADP+) in ELISA. The range of methamphetamine measurable by ELISA was 0.025-0.5 ng/well and its sensitivity was superior to that of EIA (0.3-300 ng/tube). A latex agglutination inhibition reaction test (LAIRT) was also developed for the mass screening method of urine samples. The sensitivity of this method for methamphetamine was 0.1 micrograms/ml urine.