The purpose of this study was to compare the therapeutic efficacy of a hydrocolloid dressing (Actiderm) over a medium strength corticosteroid (triamcinolone acetonide (TAA) 0.1% cream) with that of a highly potent corticosteroid (clobetasol propionate 0.05% cream) in palmo-plantar pustulosis and localized pustular psoriasis. It was a randomized, open, prospective, right-left comparative trial in 19 patients. The Actiderm dressing and the TAA cream were applied every third day, whereas the clobetasol cream was applied twice daily for 4 weeks. Both treatments resulted in a significant improvement. On completion of treatment, complete clearance was found in 13 patients (63%) with Actiderm plus TAA, but in only 3 patients (21%) with clobetasol (p = 0.001). Four weeks after stopping therapy, the clinical parameters had returned to their pre-treatment level, except for erythema on the Actiderm plus TAA treated lesions (p less than 0.05). No clinically important adverse effects were reported or observed; in particular there was no sign of skin atrophy at the end of study. The results of this study demonstrate that Actiderm applied over a medium strength corticosteroid every third day is highly effective against palmoplantar pustulosis and localized pustular psoriasis. However, it is necessary to develop treatment regimens to maintain the improvement achieved.