We have used the radioallergosorbent test (RAST) to determine IgE antibodies specific to wheat flour proteins in the sera of seven groups of patients. In some cases rye-specific IgE was also determined. Wheat and rye RAST scores showed a good correlation, presumably due to cross-reactions. Among bakers with asthma, positive scores, 0.5-3, occurred with a prevalence of 43%, and among children with eczema, scores in the range 0.5-4 were found with a prevalence of 54%. A score of 0.5 was a marginal value which was also occasionally encountered with sera from patient groups with no history of immediate hypersensitivity to wheat or rye. These groups included adults and children with allergic rhinitis and asthma, children from the general population and children with coeliac disease. The RAST appeared useful in the diagnosis of allergy to inhaled flour dust among bakers. Among children with eczema, positive wheat and rye RAST results were a common finding, which only occasionally could be linked to strong and unequivocal reactions to the foods in question. Both in bakers and children with eczema, wheat and rye RAST results showed good agreement with intracutaneous skin test results.