Ginkgo biloba extracts are used for the treatment of central and peripheral malperfusion, cerebral insufficiency and dementia. Between 1996 and 1998, several patients in Austria who had received parenteral Ginkgo extracts were reported to have developed allergy-like symptoms. The aim of the present study was to determine whether Ginkgo biloba extracts contain type I allergens. The protein content of Ginkgo biloba extracts was determined by BCA protein determination and SDS-PAGE. We used sera from 95 polysensitized plant-allergic patients (the sera contained IgE antibodies against most plant allergens), and rabbit antisera raised against defined recombinant plant allergens. The presence of allergens in Ginkgo extracts was determined by dot-blotting and Wester blot. Neither rabbit antisera nor IgE antibodies of patients reacted to the Ginkgo extracts. In addition, it was shown that prick testing of the skin could be conveniently used to study Gingko extracts for allergenic activity. In conclusion, no evidence for the presence of type I allergens in Ginkgo extracts was found. We recommend serological and/or skin testing to exclude sensitisation to components of Ginkgo biloba extracts.