Study to Assess Compliance With Long-Term Mercaptopurine Treatment in Young Patients With Acute Lymphoblastic Leukemia in Remission

Inclusion Criteria:

* Diagnosis of ALL in first remission, irrespective of risk stratification; enrollment on a Children's Oncology Group (COG) therapeutic study for ALL is not required, but the treatment plan must meet the criteria in this protocol
* Belongs to one of the four following ethnic/racial categories: African-American, Asian, Caucasian, or Hispanic; below please find definitions for these categories

  * African-American: includes patients who are African-American or of sub-Saharan black African ancestry
  * Asian: patients of Asian ancestry, including the following: Asian Indian (subcontinent), Chinese, Japanese, Korean, Native Hawaiian, Guamanian or Chamorro, Pacific Islander, Filipino, Vietnamese, Samoan, Hmong, Cambodian, Thai, Laotian, or Other Asian races
  * Caucasian: includes White or light-skinned patients of European, North African, or Middle Eastern ancestry
  * Hispanic: patients of Hispanic ethnicity, including the following: Mexican, Mexican American, Chicano, Cuban, Puerto Rican, or Other Spanish/Hispanic/Latino ethnicity
* Receiving self- or parent/caregiver-administered oral anti-metabolite chemotherapy during the maintenance/continuation phase of therapy; patients are eligible if their treatment plan calls for the following doses of 6-MP and methotrexate (MTX) during the maintenance/continuation phase: 6-MP ? 75 mg/m\^2/day orally; MTX 20 mg/m\^2/week orally;\*\* (modification of 6-MP or MTX dosing based on laboratory or clinical parameters is acceptable)

  * For guidance regarding if and when a patient being treated on or according to a specific COG (or legacy group) protocol is eligible, please refer to ?AALL03N1 Eligibility by Protocol Tool,? available in the study data forms packet on the COG website
* Has completed at least 24 weeks of maintenance/continuation chemotherapy, and is scheduled to receive at least 24 more weeks of maintenance/continuation chemotherapy\*\*

  * For guidance regarding if and when a patient being treated on or according to a specific COG (or legacy group) protocol is eligible, please refer to ?AALL03N1 Eligibility by Protocol Tool,? available in the study data forms packet on the COG website
* Written informed consent from the patient and/or the patient?s legally authorized guardian, obtained prior to registration and any study-related procedures, and in accordance with institutional policies approved by the United States (U.S) Department of Health and Human Services

Exclusion Criteria:

* Patients of multi-ethnic/multi-racial backgrounds are not eligible for this study; while patients of multi-ethnic/multi-racial ancestry (e.g., Caucasian/Japanese, Hawaiian/Puerto Rican) are not eligible, patients of mixed ancestry within a race/ethnicity (e.g., Japanese/Chinese = Asian or Korean/Japanese/Hawaiian = Asian or Mexican/Puerto Rican = Hispanic) may participate as long as they fall under the general classification of "African-American," "Asian," "Caucasian," or "Hispanic"