Thirty psoriatic out-patients were treated as a right-left comparison with dithranol (0.1, 0.5, 1, 2%) and butantrone (0.66, 1.3, 2.7, 3.9%) short contact therapy, both in white petrolatum. Fifteen of the treated patients cleared well and no obvious differences between the treated sides were clinically observed. Six patients showed some improvement, but in four of them the dithranol treated side cleared sooner and the therapy was continued with dithranol short contact therapy on both sides. In two patients the thick lesions cleared slowly and the therapy was continued with dithranol in Lassar's paste. The treatment was discontinued in nine patients: in five patients because short contact therapy was ineffective and in one patient because of strong skin irritation on both treated sides. In three patients the treatment was discontinued for non-medical reasons. Butantrone has an antipsoriatic activity almost equal to that of dithranol. When short contact treatment is used, erythema and staining with butantrone are weaker than with dithranol. Because the short contact tolerability of butantrone was good, it might be possible to start with higher concentrations.