Eleven patients with severe psoriasis were treated with hemofiltration once weekly for 4 consecutive weeks. Hemofiltration is a method of extracorporeal dialysis that uses a pressure gradient, rather than passive diffusion, to remove small and medium molecular weight substances from the blood. Six of the patients had very substantial clearing of their psoriatic lesions. Five patients had little or no apparent benefit during the course of hemofiltration treatments. They subsequently had dramatic clearing, however, when previously ineffective topical therapy was resumed. No patient had worsening of his condition during the hemofiltration series, and there were no perceived adverse effects.