Patients with active plaque psoriasis will be withdrawn from systemic and topical medications. After washout, we will select active psoriatic lesions of at least 25 square cm in size to receive either placebo ointment or a proprietary ointment containing PTH for 8 weeks. We will see the patients every 2 weeks. We will evaluate the lesions by examination and digital photography at each visit and measure parameters of calcium metabolism periodically during the 8 weeks.