Polyclonal antibodies against fumigaclavine A (FuA) were obtained from rabbits after immunization with a FuA-keyhole limpet hemocyanine conjugate prepared by formaldehyde condensation. Using these antibodies and a FuA-bovine serum albumine conjugate, a competitive indirect enzyme immunoassay (EIA) was established. The antiserum obtained from one rabbit enabled highly sensitive detection of FuA, with an IC50 level and detection limit of the standard curve of 3.3 ng/ml and approx. 1 ng/ml, respectively. The EIA was very specific for FuA, with 1.3% cross-reactivity with FuB. Several other lysergic acid derivatives (ergonovine, ergotamine, alpha-ergocryptine) were tested but did not cross-react in the FuA EIA. This is the first description of antibodies against FuA and the first development of an EIA for FuA.