Background: Psoriatic skin lesions in patients with Crohn's disease or psoriatic arthritis have shown improvement during infliximab treatment. Objective: The purpose of our study was to systematically assess the effects of infliximab in patients with psoriatic skin lesions. Methods: Eight patients with severe psoriasis were enrolled in an open-label clinical trial. Patients received infliximab, 5 mg/kg, intravenously at weeks 0, 2, and 6. The Psoriasis Area and Severity Index (PASI) was used to monitor disease activity at weeks 0, 2, 4, 6, 8, 10, and 14. Week 10 was the end point of the treatment phase; week 14 was the follow-up end point. Pruritus was assessed on a scale of 0 to 3. Histologic sections were prepared from biopsy specimens of uninvolved skin and of psoriatic lesions at weeks 0, 1, and 10 to measure epidermal thickness with the use of a microscopic micrometer grid. Results: The PASI diminished from 21.8 ± 4.2 (mean ± SE) at week 0 to 3.4 ± 2.0 at week 10, corresponding to 10.7% ± 4.3% of the original values (100%); on follow-up at week 14, the PASI was 7.1 ± 2.7 (or still 33.3% ± 11.3% of the values at week 0). Pruritus decreased from 2.5 ± 0.26 at week 0 to 0.43 ± 0.2 at week 10 and to 0.83 ± 11.3 at week 14. Likewise, epidermal thickness (acanthosis) tended to normalize from 0.41 ± 0.06 mm at week 0 to 0.14 ± 0.02 mm at week 10. No adverse effects other than fatigue during infusion on some occasions were reported. Conclusion: Although psoriasis tends to recur beyond 2 months of the infusions, this open study provides evidence that infliximab is an effective treatment. (J Am Acad Dermatol 2002;46:886-91.)