Inclusion Criteria: - Stable, active plaque psoriasis involving greater than or equal to 10% of body surface area (BSA) at screening and baseline Exclusion Criteria: - Any grade 3 or 4 adverse event or infection within 28 days before screening, or between the screening visit and study drug initiation - Evidence of skin conditions (e.g., eczema) other than psoriasis that would interfere with evaluations of the effect of study medication on psoriasis - Psoralen plus ultraviolet A radiation (PUVA), oral retinoids, cyclosporine, alefacept (Amevive®), efalizumab (Raptiva®), or any other systemic anti-psoriasis therapy within 28 days of study drug initiation - Ultraviolet light B (UVB) therapy, topical steroids, topical vitamin A or D analog preparations, or anthralin within 14 days of study drug initiation (exception: topical steroids, at no higher than moderate strength, are permitted on scalp, axillae, and groin but dose and formulation must remain stable throughout trial) - Prior exposure to any tumor necrosis factor (TNF)-inhibitor, including etanercept - Severe comorbidities - Known history of tuberculosis (TB), or previous positive purified protein derivative (PPD) test