Two Phase 3, double-blind, randomized, vehicle-controlled parallel studies evaluated the efficacy and safety of desoximetasone spray 0.25%, a super-potent topical corticosteroid, twice daily vs vehicle spray twice daily for 28 days in adult patients with moderate to severe plaque psoriasis. At baseline and throughout the study, the severity of disease for the psoriatic lesions was assessed using the Physician Global Assessment (PGA) score and a target lesion was assessed using the Total Lesion Severity Score (TLSS). A designated psoriatic plaque lesion was selected as the target lesion upon enrollment and evaluated throughout the study to determine the TLSS. To qualify for study entry, the subject needed to exhibit a PGA score of 3 (moderate) or 4 (severe) for overall disease severity, and a target lesion with an area of at least 5 cm(2) that achieved a combined score TLSS of >=7, with a plaque elevation score of >=3 (at least moderate). The mean % BSA affected by psoriasis ranged from 13%-17% at baseline. In both Phase 3 studies, a statistically significantly greater percentage of subjects in the desoximetasone spray 0.25% compared to vehicle group achieved both Clinical Success and Treatment Success at Day 28. These results, which were the primary efficacy variables, demonstrated superior efficacy in the active study group for both overall improvement of plaque psoriasis (by PGA) and in the individual psoriasis lesion (by TLSS) designated at baseline as the most severely involved plaque (target lesion). Assessment of secondary efficacy variables in both Phase 3 studies showed that subjects receiving desoximetasone Spray 0.25% twice daily exhibited statistically significantly mean changes from Baseline to Day 28 in PGA, TLSS, and % BSA affected when compared to subjects receiving vehicle spray twice daily. Tolerability and safety were assessed at all study visits. No statistically significant differences were observed between study arms and no major safety signals related to AEs were noted. No stinging and burning were reported with the spray formulation. This Class I topical corticosteroid has shown to be safe and efficacious in moderate to severe plaque psoriasis.