Inclusion Criteria: - Subjects who completed study 20030115 or 20030117 qualify to enroll into this study (provided that they meet all inclusion/exclusion criteria). - Heterosexually active men and women of child-bearing potential must agree to use a medically acceptable form of contraception throughout the study. - Subject or designee must have the ability to self-inject investigational product. - Subject must be capable of understanding and giving written voluntary informed consent. - Negative serum pregnancy test less than or equal to 14 days prior to the first dose of investigational product in all female subjects (except those surgically sterile or at least 5 years postmenopausal) Exclusion Criteria: - Active guttate, erythrodermic, or pustular psoriasis at the time of the baseline visit - Any adverse event or infection at the time of the baseline visit or at any time during the previous etanercept psoriasis study which, in the opinion of Amgen or the Investigator, would preclude participation in the study - Presence of a serious infection less than or equal to 30 days prior to the baseline visit - Evidence of skin conditions at the baseline visit (e.g., eczema) that would interfere with evaluations of the effect of investigational product on psoriasis - Previous receipt of anti-TNF agent(s) other than etanercept - Receipt of any investigational product(s), other than etanercept, less than or equal to 30 days prior to first dose of investigational product in this study - Receipt of anti-CD4 or diphtheria IL-2 fusion protein less than or equal to 24 weeks prior to first dose of investigational product in this study - Psoralen and ultraviolet A (PUVA) light therapy less than or equal to 14 days prior to first dose of investigational product in this study - Ultraviolet A (UVA) light therapy less than or equal to 14 days prior to first dose of investigational product in this study - Ultraviolet B (UVB) light therapy less than or equal to 14 days prior to first dose of investigational product in this study - Receipt of any other systemic psoriasis therapy or oral or parenteral corticosteroids less than or equal to 14 days prior to first dose of investigational product in this study - Pregnant or breast-feeding females - Significant concurrent medical conditions prior to enrollment, including: uncontrolled hypertension (defined as systolic blood pressure measurement of greater than 180 mm Hg or an untreated diastolic blood pressure of greater than 110 mm Hg); myocardial infarction less than or equal to 52 weeks prior to baseline visit; unstable angina pectoris; uncompensated congestive heart failure; severe pulmonary disease requiring hospitalization or supplemental oxygen therapy; diagnosis of multiple sclerosis or any other demyelinating disease; insulin-dependent diabetes mellitus; history of cancer (other than in-situ cervical cancer or resected cutaneous basal cell or squamous cell carcinoma) less than or equal to 5 years prior to administration of first dose of investigational product; open cutaneous ulcers; known human immunodeficiency virus (HIV), hepatitis B surface antigen (HbsAg) or hepatitis C virus (HCV) positive; any condition that might cause this study to be detrimental to the subject, in the judgment of the investigator.