Tazarotene and calcipotriol are both effective in the treatment of psoriasis. An investigator-blind, bilateral comparison of 44 lesion pairs in 19 patients was conducted to evaluate the efficacy, side effects and duration of therapeutic effects of once-daily tazarotene 0.1% gel plus petrolatum with twice-daily calcipotriol 0.005% ointment in plaque psoriasis. It consisted of a 12-week treatment phase, followed by a 4-week post-treatment observation phase. At the end of the treatment phase, tazarotene-petrolatum was as effective as calcipotriol in both objective and subjective overall efficacy assessment. Calcipotriol had a significantly greater effect in reducing erythema than tazarotene-petrolatum at weeks 2-8. At week 16, tazarotene-petrolatum demonstrated a significantly better maintenance effect in all parameters. Local irritation was noted only in tazarotene-petrolatum-treated lesions. Once-daily tazarotene 0.1% gel plus petrolatum was as effective as twice-daily calcipotriol 0.005% ointment in the treatment of plaque psoriasis, but had a better maintenance effect after the cessation of therapy.