An enzyme immunoassay for the quantitation of fmol amounts of the therapeutically important Amaryllidaceae alkaloid, galanthamine, was established. The antiserum was raised against a conjugate of galanthamine-2-O-hemisuccinate-bovine serum albumin. The antibodies used were isolated and purified by Rivanol treatment with subsequent (NH4)2SO4 precipitation. The measuring range of the assay extends from 2 to lOO pg of galanthamine, and as little as 3.5 fmol may be detected. The antibodies are highly specific for galanthamine, showing no cross reactivity with several Amaryllidaceae alkaloids. This assay allows the rapid, sensitive and precise quantitation of galanthamine in unpurified plant extracts as well as biological fluids. The galanthamine content in a variety of herbarium material as well as the frequency distribution of galanthamine in 1000 Leucojum aestivum plants from various origins in South Bulgaria have been investigated. The preliminary results demonstrate that the galanthamine-specific enzyme immunoassay can be a useful tool in medicinal plant breeding, for screening programs, as well as for taxonomic and pharmacokinetic studies.