BACKGROUND Kiwifruits have become a major elicitor of plant food allergy. Until recently, the only species of kiwifruit grown commercially was the common green-fleshed Actinidia deliciosa cv Hayward. In 1999, the yellow-fleshed cultivar Actinidia chinensis cv Hort16A was introduced into the international market. OBJECTIVE We compared the allergen compositions of green and gold kiwifruits and assessed the sensitization patterns of patients with kiwifruit allergy toward both varieties. METHODS Sera from 90 patients with kiwifruit allergy from Austria, central Italy, and the Netherlands were tested for IgE binding to green and gold kiwifruit protein extracts and to purified actinidin, the major kiwifruit allergen, by ELISA. In addition, ELISA inhibitions and immunoblots were performed with selected sera. Relevant allergens were identified by N-terminal sequencing and immunoblotting with allergen-specific antibodies. RESULTS IgE immunoblotting showed marked differences in the allergen compositions of green and gold kiwifruit extracts. Phytocystatin, a novel plant food allergen, and a thaumatin-like protein were identified as allergens common for both cultivars. Two allergens with homologies to chitinases were found in gold kiwifruits, whereas actinidin was detected exclusively in green kiwifruits. Patients from Central Europe and central Italy showed distinct sensitization profiles toward green and gold kiwifruit extracts as well as actinidin. Whereas sera from Austrian and Dutch patients mainly recognized green kiwifruit extract and actinidin, almost all Italian sera showed IgE binding to both kiwifruit species, but only half of them contained actinidin-specific IgE. Green and gold kiwifruit extracts were shown to be highly cross-reactive as determined by IgE ELISA inhibition. CONCLUSION The presence of common allergens and the IgE cross-reactivity to green kiwifruit qualifies gold kiwifruit as a potential new allergen source for patients allergic to green kiwifruits.