Inclusion Criteria:

- Age ≧18 years.

- Performance status of 0 to 1 on the Eastern Cooperative Oncology Group (ECOG)
Scale.

- Patients with histologically or cytological-proven non-small cell lung cancer.

- Stage IIIA or IIIB, excluding those with pericardial, pleural effusion, and those
with contralateral hilar or contralateral supraclavicular lymph nodes.

- Patients must have measurable disease according to RECIST criteria, and all
detectable tumor can be encompassed by radiation therapy fields.

- Weight loss ≦ 5% in the previous six months.

- Patient must have adequate blood, liver, lungs and kidney function within the
requirements of this study.

- Female patients of child-bearing potential must test negative for pregnancy at the
time of enrollment based on a serum pregnancy test. Male and female patients must
agree to use a reliable method of birth control during and for 3 months following the
last dose of study drug.

- Patients must sign a study-specific informed consent form prior to study entry.

Exclusion Criteria:

- Undifferentiated small cell carcinoma, any stage.

- Complete tumor resection, recurrent disease, or those patients eligible for
definitive surgery.

- Stage IV.

- Age <18 years.

- Performance status ≧2 on the Eastern Cooperative Oncology Group (ECOG) Scale.

- Previous chemotherapy or previous biologic response modifiers for current lung
cancer.

- Patient has previously had thoracic radiation therapy.

- Have received treatment within the last 30 days with a drug that has not received
regulatory approval for any indication at the time of study entry.

- Prior or concurrent malignancy except non-melanomatous skin cancer unless
disease-free for five years or more.

- Serious concomitant disorders that would compromise the safety of the patient, or
compromise the patient's ability to complete the study, at the discretion of the
investigator.

- History of significant neurological or mental disorder, including seizures or
dementia.

- Inability to interrupt aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs)
2 days before, the day of, and 2 days after the dose of pemetrexed. If a patient is
taking an NSAID (Cox-2 inhibitors included) or salicylate with a long half-life (e.g.
naproxen, piroxicam, diflusinal, nabumetone, rofecoxib, or celecoxib) it should not
be taken 5 days before, the day of, and 2 days after the dose of pemetrexed.

- Inability or unwillingness to take folic acid, vitamin B12 supplementation, or
dexamethasone.

- Pregnant or lactating females.