Skin prick test reactivity to commercial and self-made feather-allergen extracts was examined in 269 consecutive adult patients with suspected allergic cutaneous or respiratory symptoms who had been referred to a university clinic. Some 177 subjects reacted to any inhalant allergen. Twenty-four (9% of the whole group and 14% of those positive to any inhalant allergen) reacted to commercial feather extracts from ALK (Hørsholm, Denmark), and 51 to any of the seven feather extracts used. Feather-mix RAST (Pharmacia, Sweden) was positive in three cases only. Skin prick test or CAP-RAST or both to house-dust mite were positive in 16 of those 24 subjects positive to the commercial feather extracts, but in only 23 of the 150 other atopic subjects (P < 0.001). A nasal challenge with a feather extract was made in 20 cases, always with negative result. In immunospot studies, concomitant allergy to feather-allergen extracts and house-dust mite could be demonstrated. Mite allergens in feather extracts were verified in RAST-inhibition studies. A clinically significant feather allergy was found in one patient only. The results suggest that true feather allergy is very rare, and most of the positive reactions seen in skin prick tests to feather extracts are probably caused by mite allergens present in feathers.