We investigated sera of 12 patients with IgE-mediated hypersensitivity reactions to potato, using different in vitro methods. Radioallergosorbent test classes 2-4 (7.6-46.5% binding) were measured with potato allergen disks. Immunoblot detected allergen bands with an isoelectric point range of approximately 4.5-5.2 and mainly in a molecular weight range between 16.00 and 30.00 kD. But also at molecular weights of 43.00 and 65.00 kD allergen bands (IgE specificities) could be detected. Histamine release assay performed with isolated fractions of the potato extract showed a great individual variation and positive results of fractions of molecular weights between 10.00 and 80.00 kD. From our data we conclude that raw potato is a 'multiallergenic' vegetable.