SUMMARYClobetasone butyrate 0.05% (Eumovate), a halogenated topical steroid, was compared with hydrocortisone butyrate 0.1% (Locoid) which does not contain any halogen atoms. In the treatment of eczema there was no difference between the preparations, but in that of psoriasis the halogen‐containing steroid was significantly more effective. Under normal circumstances neither preparation had any detectable effect on adrenal function, but with large doses under total‐body polythene occlusion, circulating cortisol levels were reduced less by the halogenated than by the non‐halogenated preparation.Corticosteroids which contain a halogen atom are often considered to cause more adverse effects than the non‐halogenated preparations with similar clinical efficacy. This study shows that this cannot be assumed for their ability to suppress cortisol