Inclusion Criteria:

- Patients must have documented adenocarcinoma of the prostate, treated with androgen
suppression, and now present with a rising PSA .

- Prior therapy with hydrocortisone is allowed (must have discontinued > 4 weeks prior
to study treatment). Prior use of ketoconazole for prostate cancer treatment is
allowed (must have discontinued > 4 weeks prior to study treatment).

- Prior therapy with chemotherapy is allowed if it was administered as neoadjuvant or
adjuvant therapy related to primary treatment and was completed > 6 months prior to
starting study treatment.

- Testosterone level < 50 ng/dl within 4 weeks prior to study treatment. Patients who
have not undergone surgical castration must continue primary androgen suppression
therapy (luteinizing hormone-releasing hormone [LHRH] agonist) while on protocol
therapy.

- Patients may be receiving oral bisphosphonate therapy prior to study treatment and
continue while receiving treatment, but must not begin treatment with bisphosphonate
while receiving study treatment. Patients on oral bisphosphonates must have
completed at least 4 weeks of bisphosphonate therapy prior to study treatment.

- Patients must have adequate major organ function. All values must be obtained
within 4 weeks prior to study treatment.

- Creatinine < 1.7 mg/dL or a creatinine clearance > 50 mL/min,

- SGOT (AST), SGPT (ALT) < 2X the institution's upper limit of normal,

- Bilirubin < 1.5 mg/dL,

- ANC > 1500/mm3,

- Platelet (PLT) > 100,000/mm3

- Patients must have Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or
1.

- Patients must be > 18.

- Patients taking warfarin are eligible.

- Patients taking CYP3A4 inducers or inhibitors are eligible.

- Patients with a history of prior malignancy are eligible provided they were treated
with curative intent and have been free of disease for the time period considered
appropriate for the specific cancer.

Exclusion Criteria:

- No previous palliative radiation. Prior radiation to the primary site is allowed.

- HIV positive patients receiving combination anti-retroviral therapy are excluded
from the study because of possible pharmacokinetic interactions with erlotinib.

- Patients with gastrointestinal tract disease resulting in an inability to take oral
medication are ineligible.

- Patients must not have ongoing or active infection, symptomatic congestive heart
failure, unstable angina pectoris, symptomatic cardiac arrhythmia, or psychiatric
illness that would limit compliance with study requirements.

- Patients must not have received prior targeted therapy, including no prior EGFR
inhibitor.

- Patients must not have evidence of metastatic disease.