Inclusion Criteria:

- Patient must have an ECOG/Zubrod performance status of =< 2

- Patient must have a histologic diagnosis of primary GIST (without peritoneal or
distant metastasis) that expresses Kit protein by immunohistochemistry and have tumor
size >= 3cm in maximum dimension

- Patient must have undergone complete gross resection (includes R0 [negative
microscopic margins] and R1 [positive microscopic margins]) of a primary GIST within
70 days prior to registration

- Patient must have a chest x-ray completed within 28 days prior to registration; NOTE:
Chest CT within 28 days prior to registration can be used in lieu of chest x-ray

- Patient must have a post-operative CT scan with IV and PO contrast or MRI with
contrast (if allergic to CT contrast) of abdomen and pelvis within 28 days prior to
registration

- Creatinine =< 1.5 times the institution ULN

- WBC >= 2,000/mm^3

- Platelets >= 100,000/mm^3

- Total Bilirubin =< 1.5 times the institution ULN; NOTE: Patients with elevated
bilirubin secondary to Gilbert's disease are eligible to participate in the study

- AST =< 2.5 times the institution ULN

- ALT =< 2.5 times the institution ULN

- Female of childbearing potential must have negative serum pregnancy test; NOTE:
Post-menopausal women must be amenorrheic for at least 12 months to be deemed not of
reproductive potential

- Patient or the patient's legally acceptable representative must provide a signed and
dated written informed consent prior to registration and any study-related procedures

- Patient must provide written authorization to allow the use and disclosure of their
protected health information; NOTE: This may be obtained in either the study-specific
informed consent or in a separate authorization form and must be obtained from the
patient prior to study registration (non-US sites are exempt from HIPAA regulations)

- If patient is a cancer survivor, ALL of the following criteria apply:

- Patient has undergone potentially curative therapy for all prior malignancies

- No evidence of any prior malignancies for at least 5 years with no evidence of
recurrence (except for effectively treated basal cell or squamous carcinoma of
the skin, carcinoma in-situ of the cervix that has been effectively treated by
surgery alone, or lobular carcinoma in-situ of the ipsilateral or contralateral
breast treated by surgery alone)

- Patient is deemed by their treating physician to be at low risk for recurrence
from prior malignancies

Exclusion Criteria:

- Patient has received post-operative chemotherapy

- Patient has received post-operative radiation therapy

- Patient has received post-operative investigational treatment

- Patient has received prior therapy with STI571

- Patient has had an active infection requiring antibiotics within 14 days prior to
registration

- Patient has objective evidence of residual disease on the postoperative CT scan or
MRI of the abdomen or pelvis

- Patient, if female and breastfeeding; NOTE: It is not known whether STI571or its
metabolites are excreted in human milk; however, in lactating female rats
administered 100mg/kg, a dose approximately equal to the maximum clinical dose of
800mg/day based on body surface area, STI571 and /or its metabolites were extensively
excreted in milk; it is estimated that approximately 1.5% of a maternal dose is
excreted into milk, which is equivalent to a dose to the infant of 30% the maternal
dose per unit body weight; women should be advised against breastfeeding while taking
STI571

- Patient has New York Heart Association class 3 or 4 cardiac disease

- Patient is taking full dose warfarin; NOTE: The use of mini-dose warfarin (1mg orally
per day) for prevention of central line-associated deep venous thrombosis is
permitted