Inclusion Criteria:

- Rheumatoid arthritis (RA), psoriatic arthritis (PsA), or ankylosing spondylitis (AS)
diagnosed according to established criteria.

- Persistent moderate (grade 2) or severe (grade 3) swelling due to inflammatory
arthritis in at least one peripheral joint eligible for injection.

- For subjects with RA, an adequate trial of at least one disease-modifying drug
(DMARD) prior to screening.

- For subjects currently on DMARD(s), a stable regimen of inflammatory arthritis for
the previous three months, with no changes in doses four weeks prior to screening.

- Age greater than 18 years and less than 75 years at the time of screening.

- Willingness to practice effective birth control measures during the study (through
week 36), if male or female of reproductive ability.

- Able to give written informed consent.

Exclusion Criteria:

- Disease severe enough to warrant a change in regimen for inflammatory arthritis in
the next three months.

- Discontinuation of etanercept in the past because of safety concerns.

- Current use of anakinra (Kineret®)or abatacept (Orencia®).

- Corticosteroid therapy at doses higher than the equivalent of 10 mg prednisone per
day.

- Steroid or hyaluronate injection in the target joint or receipt of an investigational
agent less than four weeks prior to screening.

- Class IV ACR functional status (Hochberg et al., 1992).

- Any of the following laboratory values: Hemoglobin <8.5 gm/dL, white blood cell count
<3500 per mm cube, platelet <100 K/uL, creatinine >2 mg/dL, bilirubin >2 mg/dL, AST
or ALT >2 times the upper limit of normal, or abnormal coagulation profiles (>2
seconds beyond upper range of normal PT or PTT).

- Known HIV infection, known hepatitis C infection, or known positive serologic test
for hepatitis B surface antigen.

- Positive PPD, unless previously treated with appropriate prophylaxis.

- Pregnancy or lactation, either at the time of screening or planned in the next 18
months.

- Inflammatory bowel disease, such as Crohn's disease or ulcerative colitis.

- Serious medical disease, such as severe liver or kidney disease, uncompensated
congestive heart failure, myocardial infarction within six months, unstable angina,
uncontrolled hypertension, severe pulmonary disease or uncontrolled asthma,
demyelinating neurological disease, history of cancer (other than cutaneous basal and
squamous cell carcinoma) with less than five years documentation of a disease-free
state, insulin-dependent diabetes, recurrent opportunistic infections or other
concurrent medical condition that, in the opinion of the investigator, would make the
subject unsuitable for the study.

- Unlikely to comply with protocol.