Although tazarotene monotherapy is generally efficacious and well tolerated, studies show that both the efficacy and the tolerability of tazarotene therapy can be further improved when it is used in combination with certain topical corticosteroids. The studies reported here evaluate the usefulness of two potential combination regimens. In one regimen, a corticosteroid is added to tazarotene treatment. In the other regimen, corticosteroid treatment alternates on a daily basis with tazarotene treatment. The results of the first study, which involved 300 patients, showed that additive combination therapy using tazarotene plus a mid- or high-potency topical corticosteroid significantly increased the percentage of plaques achieving treatment success at the end of the treatment period, compared with tazarotene plus placebo (91% and 95% vs. 80%, respectively; P<0.05 for both). Similarly, tazarotene plus a mid- or high-potency topical corticosteroid reduced the incidence of patient withdrawals compared with tazarotene plus placebo (5.5% and 9.6% vs. 13.3%). The results of the second study, which involved 398 patients, showed that a combination regimen that alternates between tazarotene and a high-potency topical corticosteroid treatment each day, significantly increased the treatment success rate compared with regimens using tazarotene alternating with a mid-potency corticosteroid or placebo (75% vs. 55% and 54%, respectively, at the end of the treatment period; P<0.05 for both). In addition, there was a trend towards a lower incidence of treatment-related adverse events as corticosteroid potency increased (from 42% with tazarotene plus placebo to 36%, 32%, and 31% with tazarotene plus the low-, mid-, and high-potency corticosteroid, respectively). Both treatment regimens are potentially useful and offer a rational approach to optimizing the efficacy and tolerability of tazarotene treatment for plaque psoriasis.