Antifungal drugs have been reported to have efficacy in the treatment of seborrhoeic disorders. This phenomenon has been attributed to their effects againstPityrosporum ovalewhich is often present on the diseased skin. In the present double-blind study, 74 patients with seborrhoeic dermatitis of the scalp with typ-ical symptoms such as scaling, erythema and itching, were randomly allocated to 4-weeks' treatment with clotrimazole—hydrocortisone liniment, hydrocortisone or plain propylene glycol-containing liniment base. In addition to symptoms, the presence ofP. ovalewas determined before and after treatment. All main symptoms were markedly relieved in all treatment groups. The area affected was clearly reduced in most patients after weeks' treatment. There were no statistically significant differences between treatments in any parameter evaluated. In the final global assessment, the number of patients with a good response was highest in the clotrimazole-hydrocortisone treatment group: 84% vs. 77% in the hydrocortisone group. However, the number of cured patients was the same (76%) in the liniment base group. The area of affected skin decreased during the treatment in most patients: 60% of all patients had at the most 5% of the initial area left. Data from the culture of P.ovulewas evaluable from 54 patients. In only 14 cases, of which 5 were in the clotrimazole—hydrocortisone group, did the culture become negative after treatment. Eight patients discontinued the treatment prematurely; four due to lack of efficacy (three in the clotrimazole-hydrocortisone and one in the hydrocortisone group), one because of severe itching of the scalp (liniment base group) and three for other reasons. In conclusion, treatment of seborrhoeic dermatitis with plain hydrocortisone was as effective as the combination of clotrimazole and hydrocortisone. However, propylene glycol-containing liniment base was about as effective as the liniment with active drugs. The clinical results did not correlate well withP. ovulecultures.