Inclusion Criteria:

1. Must give written informed consent.

2. Must have had moderate, moderately severe or severe chronic plaque psoriasis as
determined by the investigator prior to initial treatment (baseline) with AMEVIVE.

3. Must be 18 years of age or older.

4. Must have completed a standard 12-week course of AMEVIVE and have received at least
10 doses.

5. Response to current AMEVIVE therapy must be less than a desired response as
determined by the physician, and subject and some residual psoriasis must be present.

Exclusion Criteria:

1. Female subjects who are not postmenopausal for at least 1 year, surgically sterile,
or not willing to practice effective contraception during the study.

2. Nursing mothers, pregnant women, and women planning to become pregnant

3. Current enrollment in any investigational study in which the subject is receiving any
type of drug, biologic, or non-drug therapy.

4. Treatment with another investigational drug, or approved therapy for investigational
use, within 3 months of investigational drug administration.

5. Treatment with systemic retinoids, systemic steroids, methotrexate, cyclosporine,
azathioprine, thioguanine, etanercept, efalizumab, infliximab, adalimumab or
mycophenolate mofetil or other systemic immunosuppressant agents within 4 weeks of
investigational drug administration.

6. Treatment with Ultraviolet B (UVB) phototherapy or Psoralen + Ultraviolet A (PUVA),
within 4 weeks of investigational drug administration.

7. Serious local infection (e.g., cellulitis, abscess) or systemic infection (e.g.,
pneumonia, septicemia) within the 3 months prior to the first dose of investigational
drug.

8. History of >3 cutaneous squamous cell carcinomas or any systemic malignancy.

9. Skin lesions suspicious for malignancy.

10. Known HIV, viral hepatitis, or tuberculosis infection.

11. History of severe allergic or anaphylactic reactions.

12. ALT or AST greater than three times the upper limit of normal.

13. Significantly abnormal hematology (hemoglobin, hematocrit, platelets, white blood
cells), as determined by the investigator.

14. CD4+ T lymphocyte count at screening visit less than 250 cells/mm3.

15. Known hypersensitivity to AMEVIVE or any of its components.

16. Subject's inability to comply with study requirements.