Eighteen patients with psoriatic arthritis were treated for 48 hours with an infusion of somatostatin 250 micrograms/hr diluted in a 5% glucose solution. This therapy led to a reduction of joint pain and satisfactory clearing of cutaneous lesions immediately after treatment in eight patients, less marked results in four, and null in four. Two patients were dropped from the study because of negative side effects during administration of the drug. Fifteen days after treatment, the clearing of lesions and joint pain reduction were even more pronounced. The most encouraging results were obtained on erythrodermic and large plaque psoriasis and on the polyarticular involvement. We suggest that the use of this drug, whose side effects are discussed, should be limited to patients with polyarthritis showing severe cutaneous involvement.