The effects of acitretin (free acid of etretinate) on the serum lipoprotein pattern and on the fat elimination in serum of 8 patients with psoriasis and 4 with palmo-plantar pustulosis were studied. The drug was given for 12 weeks; the average daily dose was 40 mg. Lipoprotein analyses and an intravenous fat tolerance test (IVFTT) were performed on three occasions (before, after 8 weeks' treatment, as well as 8 weeks after the end of the treatment). Acitretin increased the triglyceride concentration of the very low density lipoproteins by about 50% (p less than 0.02) and reduced the cholesterol of the high density lipoproteins significantly (p less than 0.001), leading to an increased low density/high density lipoprotein cholesterol ratio (p less than 0.02). The IVFTT indicated a lowering of the fat elimination capacity. All changes reverted to the original values after an 8-week wash-out period. The data suggest that the effects of acitretin on the lipoprotein metabolism resemble those of etretinate and isotretinoin.