Background: Topical therapy providing initial improvement and maintenance of effect after treatment of the large majority of patients with limited, mild to moderate psoriasis is not presently available. Previous topical retinoids have generally been either ineffective or too irritating for therapy of psoriasis. Objective: Our purpose was to evaluate a new topical retinoid, tazarotene, in the treatment of stable plaque psoriasis during treatment and posttreatment periods. Methods: In a double-blind manner, 324 patients were randomly selected to receive tazarotene 0.1% or 0.05% gel, or vehicle control, once daily for 12 weeks and were then followed up for 12 weeks after treatment. Results: Of the total, 318 patients could be evaluated. Tazarotene gels were superior ( p < 0.05) to vehicle, often as early as treatment week 1, in all efficacy measures: plaque elevation, scaling, and erythema; treatment response; percentage treatment success (patients with ≥50% improvement); and time to initial success. Efficacy was equivalent on target lesion sites (trunk or limbs and knees or elbows) and overall. A sustained therapeutic effect was observed for 12 weeks after treatment. Tazarotene gel was cosmetically acceptable. There was low systemic absorption, limiting toxicity to local irritation. Conclusion: Once-daily tazarotene was effective and safe as a topical monotherapy for plaque psoriasis, providing rapid reduction of signs and symptoms. (J Am Acad Dermatol 1997;37:85–92.)