A total of 50 patients with psoriasis vulgaris who showed an unsatisfactory response to etanercept 50 mg twice a week followed by 50 mg once a week and a total of 50 patients who showed an unsatisfactory response to etanercept 50 mg twice a week without dose reduction will be recruited. All patients will receive adalimumab 40 mg every other week (EOW) for 12 weeks. Patients who fail to reach a physician's global assessment (PGA) of clear or almost clear at week 12 will have an increase in adalimumab to 40 mg every week (EW) for an additional 12 weeks. Patients who reach a PGA of clear or almost clear at week 12 will continue to receive adalimumab at 40 mg EOW for an additional 12 weeks. Patients will be evaluated for safety and efficacy every 4 weeks for a total of 24 weeks. PASI, BSA and PGA will be performed at each visit. Routine chemistry, hematology and urinalysis will be performed every 4 weeks.