Background Peanut is the most common cause of severe or fatal food-associated anaphylaxis. Studies indicate that peanut extracts contain many allergenic proteins. The identification of major and minor allergenic components is necessary for standardization of experimental and diagnostic extracts. Objective To identify further major and minor allergenic components of peanut extract using a large population of peanut allergics, and to relate serological findings to clinical parameters. Methods The crude peanut extract was fractionated by fast protein liquid chromatography and the IgE binding proteins identified by sodium dodecyl sulphate polyacrylamide gel electrophoresis followed by western blotting. Serum from 89 peanut allergics with a positive history of peanut allergy and elevated specific IgE and control serum from four atopic and four non-atopic, non-peanut allergics were used. Results Nineteen peanut proteins were found to bind IgE from peanut allergic sera. Over 70% of subjects reacted to protein bands of 63 and 17 kDa (consistent with Ara h 1 and Ara h 2, respectively), confirming the importance of these two proteins as major allergens. A high proportion of patient sera also bound proteins at 15, 10, 30, 18 and 51 kDa in decreasing order. The percentage of cases with sensitivity to a 15 kDa protein was found to be higher in patient groups with severe reactions to peanut. Conclusion This study highlights the diversity of peanut allergens. Diagnostic extracts containing a high proportion of the 15 kDa component may aid in diagnosis.