The objective of this study was to test the effect of a commercial, preserved, but otherwise untreated Aloe vera gel in psoriasis. Forty-one patients with stable plaque psoriasis were included in a randomised, double-blind, placebo-controlled right/left comparison. The study comprised a 2-week washout period followed by a 4-week treatment period with two daily applications and follow-up visits after 1 and 2 months. Data on 40 patients were analysed. The score sum of erythema, infiltration and desquamation decreased in 72.5% of the Aloe vera-treated sites compared with 82.5% of the placebo-treated areas from week 0 to week 4, which was statistically significant in favour of the placebo treatment. Fifty-five per cent of the patients reported local side-effects, mainly drying up of the skin on test areas.