Inclusion Criteria:

- Histologically confirmed advanced (stage IV) or recurrent adenocarcinoma of the colon
or rectum

- Must have available tissue for immunohistochemical analysis

- At least one unidimensionally measurable lesion

- At least 20 mm by conventional techniques OR at least 10 mm by spiral CT scan

- Tumor marker (carcinoembryonic antigen) elevation alone is insufficient for
study entry

- No known brain metastases

- Performance status - ECOG 0-2

- Granulocyte count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

- Bilirubin no greater than 1.5 times upper limit of normal (ULN)

- AST less than 2 times ULN (5 times ULN if liver involvement of tumor)

- Creatinine no greater than 1.5 times ULN

- No symptomatic congestive heart failure

- No unstable angina pectoris

- No cardiac arrhythmia

- Not pregnant or nursing

- Fertile patients must use effective contraception

- HIV negative

- No other severe or uncontrolled concurrent illness that would adversely impact the
safety or efficacy of study therapy

- No ongoing or active infection

- No other prior malignancy unless curatively treated and no evidence of recurrence

- No history of allergic reactions attributed to compounds of similar chemical or
biologic composition to gefitinib

- No psychiatric illness or social situation that would preclude study compliance

- No prior chemotherapy for advanced disease

- More than 4 weeks since other prior chemotherapy (6 weeks for nitrosoureas or
mitomycin) and recovered

- More than 4 weeks since prior radiotherapy and recovered

- At least 6 months since prior adjuvant therapy

- No prior epidermal growth factor receptor inhibitor

- No other concurrent investigational agents

- No other concurrent anticancer therapy

- No concurrent phenytoin, carbamazepine, barbiturates, rifampin, rifapentine,
oxacarbazepine, modafinil, griseofulvin, or Hypericum perforatum