Ten adult patients with a medical history of immediate allergic reactions following ingestion of minute amounts of codfish were examined together with 27 control subjects (8 nonatopics, 7 pollen allergics, and 12 suffering from atopic dermatitis) all regularly ingesting codfish without experiencing reactions. All 37 subjects were evaluated by skin prick test, RAST, and histamine release test in order to determine the value of these commonly used diagnostic tests. The results were compared to titrated, oral, double-blind, placebo-controlled food challenges (DBPCFCs) with fresh codfish undertaken in the 10 patients, whereas all control subjects were classified as challenge-negative according to their questionnaires. Totally, 7 of 10 medical histories were confirmed by DBPCFC, and in these most of the reported symptoms proved reproducible. Oropharyngeal itching and swelling occurred as the first symptom, always preceding the onset of any accompanying symptom. For identification of DBPCFC-positive subjects, skin prick test and RAST proved to be the most sensitive tests (7/7), and all tests showed specificities of 90-97%. The skin prick test still seems reliable but does not, however, exclude the need for DBPCFC.