Extract of wheat flour obtained by extraction, centrifugation and dialysis was immunochemically characterized by quantitative immunoelectrophoresis using rabbit antibodies. The analysis revealed wheat flour to be composed of 40 antigens, some of which were immunologically partially identical with antigens of rye flour and of common grass pollen. Furthermore, antigens of the gliadin fraction of wheat flour were identified. 25 bakers with allergic complaints working in and around Copenhagen were clinically tested with wheat flour and related extracts. Among 13 bakers with respiratory complaints (asthma and/or rhinitis), 11 showed positive reactions to wheat flour extract when tested in histamine release from basophil leukocytes radioallergosorbent test and skin test, whereas further 2 were positive in the basophil test only. The ability of the IgE of individual sera to adsorb to the individual antigens of wheat flour was examined by means of crossed radioimmunoelectrophoresis. On the basis of these results, individual allergenic components of wheat flour were identified, three of these with comparatively high affinity and frequency.