Inclusion Criteria:

- Patients must have pathologically confirmed SCLC at MSKCC that has progressed after
one or two chemotherapy regimens.

- At least 3 weeks must have elapsed since last chemotherapy or radiation treatment and
initiation of study treatment.

- Karnofsky performance status > or = to 60%.

- Patients must have measurable disease, this can include brain metastases.

- Patients must have normal organ and marrow function as defined below:

- − leukocytes > 3,000/mcL

- platelets > 100,000/mcL

- total bilirubin < 1.5 mg/dL

- AST(SGOT)/ALT(SGPT) < 2.5 X institutional upper limit of normal

- Creatinine < 2.0 mg/dl

- For women of child-bearing potential, negative pregnancy test within 7 days prior to
starting temozolomide.

- Men and women of childbearing potential must agree to practice adequate
contraception.

- Ability to understand and the willingness to sign a written informed consent
document.

- Both men and women of all races and ethnic groups are eligible for this trial.

Exclusion Criteria:

- Patients who have not recovered from adverse events of previous therapies.

- Patients receiving other investigational agents.

- Patients with leptomeningeal involvement.

- Uncontrolled intercurrent illness including, but not limited to, ongoing or active
infection, symptomatic congestive heart failure, unstable angina pectoris, or
psychiatric illness/social situations that would limit compliance with study
requirements.

- Acquired Immune Deficiency Syndrome (AIDS) based upon current CDC definition or
HIV-positive patients on combination antiretroviral therapy. However, HIV testing is
not required for entry into this protocol. The need to exclude patients with AIDS
from this protocol is necessary because these patients are at increased risk of
lethal infections when treated with marrow- suppressive therapy. Excluding patients
on HAART is necessary due to the potential for pharmacokinetic interactions with
temozolomide.

- Women who are pregnant or breast feeding, due to possible adverse effects on the
developing fetus or infant due to study drug.