It has been postulated that anomalous cerebral dominance is associated with disorders of the immune system and increased incidence of autoimmune diseases has been reported in left-handed individuals. In this study, 313 patients attending an allergy clinic were assessed for left- and right-handedness, using the Edinburgh Handedness Inventory. The results were compared to those in 350 age- and sex-matched control individuals. It was found that significantly more (P less than 0.02) left-handers than right-handers attended the clinic. Among atopic patients in general, patients with IgE-mediated symptoms, patients with urticaria and patients with eczema, there was a highly significant increase in left-handers (P less than 0.005). The results are discussed in terms of dominance.