KH 1060 is a 20-epi-vitamin D3 analogue, structurally related to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). In vitro, KH 1060 is much more potent than 1,25(OH)2D3 in regulating cell growth and T lymphocyte mediated immune responses, despite a similar calcemic activity in vivo. Therefore, KH 1060 is of potential interest in the treatment of psoriasis and other diseases characterized by accelerated cell growth and T lymphocyte activation. In a multicenter, prospective, randomized, double-blind, vehicle-controlled right/left comparative study, patients with plaque-type psoriasis vulgaris were randomly assigned to one of the following treatment groups: (I) KH 1060 ointment 0.2 microgram/g versus placebo ointment, (II) KH 1060 ointment 0.2 microgram/g versus KH 1060 ointment 0.04 microgram/g, and (III) KH 1060 ointment 0.2 microgram/g versus KH 1060 ointment 1 microgram/g. All treatments were given twice daily for 6 weeks. Sixty-four of the 70 randomized patients completed the study. At the end of treatment, no difference was demonstrated between KH 1060 0.04 microgram/g and vehicle, whereas significantly increasing improvement was found for the doses KH 1060 0.2 microgram/g and KH 1060 1 microgram/g. According to the investigator's overall assessments at the end of treatment, KH 1060 1.0 microgram/g and KH 1060 0.2 microgram/g produced a marked or moderate improvement in most patients. Mild lesional irritation was observed after treatment with KH 1060 as well as with placebo. One patient was withdrawn because of an eczematous reaction, where KH 1060 1.0 microgram/g was applied.(ABSTRACT TRUNCATED AT 250 WORDS)