A previous study of patients with allergic contact dermatitis yielded results which supported the hypothesis that the presence of certain HLA antigens led to a predisposition to allergen-specific reactions and others to multiple contact sensitivity. The present study was performed to test this hypothesis. 129 patients sensitive to one allergen only (either chromium, nickel, formalin or balsam of Peru) and 83 patients sensitive to two or more allergens were HLA typed regarding the A and B loci. A series of 368 persons matched with regard to sex, age and place of residence were used as controls. A tendency towards an association between HLA B7 and contact allergy was observed. No other data confirming the hypothesis mentioned above were obtained. Among 37 patients who also had atopic diathesis a decreased frequency of HLA B7 was found.