We have produced monoclonal antibodies against artelinic acid and investigated the reactivity with artemisinin drugs and metabolites. Antibody F170-10 is fairly specific for artelinic acid but does bind artemisinin and artemether (3-5% cross-reactivity). Dihydroartemisinin, artesunate, and metabolites of artemisinin showed less reactivity. With this antibody, an inhibition ELISA has been set up to detect artemisinin compounds in urine. In healthy subjects who received a single oral dose of artemisinin, artemether, artesunate or dihydroartemisinin, ELISA reactivity in urine was found. This reactivity in urine paralleled the plasma concentrations of artemether and dihydroartemisinin. The results show that this immunoassay for artelinic acid can be used to detect artemisinin compounds in urine for about 8 hr after intake. With a more sensitive test, this simple method as a urine dipstick may be become useful for drug use and compliance studies in malaria-endemic areas where the artemisinin derivatives are increasingly used.