Incidence of psoriasis vulgaris in Asians is estimated at 0.05-0.3%. Studies in North America and Europe demonstrated that adalimumab, a fully human, recombinant, immunoglobulin G(1) monoclonal antibody, was efficacious and well-tolerated in patients with chronic plaque psoriasis. This 24-week, placebo-controlled study evaluated the efficacy and safety of three different dosing regimens of adalimumab in Japanese patients with moderate to severe chronic plaque psoriasis (n = 169). Patients were randomized to receive adalimumab 40 mg every other week (eow), adalimumab 80-mg loading dose at week 0 followed by adalimumab 40 mg eow starting at week 2, adalimumab 80 mg eow, or placebo eow given as s.c. injections. The primary efficacy endpoint was the percentage of patients achieving a 75% or greater improvement in Psoriasis Area and Severity Index (PASI 75) score at week 16. At week 16, PASI 75 response rates were significantly greater for all three adalimumab groups (40 mg eow: 57.9%, P < 0.001; 40 mg eow plus loading dose: 62.8%, P < 0.001; 80 mg eow: 81.0%, P < 0.001) versus placebo (4.3%). As early as week 4, the 40-mg eow plus loading dose and 80-mg eow groups achieved significantly greater PASI 75 response rates compared with placebo. Injection-site reactions and hepatic events occurred in greater percentages of adalimumab-treated patients compared with placebo. Adalimumab therapy demonstrated efficacy and safety at all three dosage regimens. Rapid response rate in patients receiving 40 mg eow plus loading dose supports using an 80-mg loading dose in the treatment of psoriasis.