Fifty patients with psoriasis were treated with short-term dithranol therapy. This therapy is based upon the different kinetics of penetration of dithranol in healthy and damaged skin. In inpatients once a day 1% dithranol-5% salicylic acid vaseline was applied to all parts of the skin and after 5-10 min washed off thoroughly. Within a few days the dosage was increased to 3% dithranol and the application time to 20 min if possible. The treatment was continued on an individual tolerance basis. In contrast to the in-patients, the out-patients were treated according to plan with weekly increases of dithranol concentration from 1-3% and an application time from 5-20 min. Thirty-two patients (17 in-patients, 15 out-patients) showed a good response, in 12 cases (5 in-patients, 7 out-patients) the response was fair and in 6 cases (2 in-patients, 4 out-patients) the response was poor. Short-term dithranol therapy seems to be superior to the conventional therapy with dithranol. Its advantages are the absence or insignificance of irritability of the healthy skin surrounding the psoriatic plaques, and the economy of time and expense.