Inclusion Criteria:  The patient must have a diagnosis of acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML). Stored diagnostic pre-treatment samples corresponding to the patient's original diagnosis of leukemia must be available for request from either the COG Biopathology Center or a treating institution The patient must be enrolled on APEC14B1 with consent to future contact and indicate that cord blood was stored at birth in the APEC14B1 registry intake data. The patient must also have been registered with COG by a North American (limited to the U.S. and Canada) member institution. ≤ 25 years old at the time of original diagnosis with ALL or AML The patient must be able to understand written and spoken English or Spanish All patients must provide their consent/assent, as appropriate, and for patients under the age of majority at least one parent or legal guardian must provide consent as well All institutional, FDA, and NCI requirements for human studies must be met  Exclusion Criteria:  Patients who responded that cord blood was not stored at birth are excluded. Patients without stored diagnostic, pre-treatment leukemia samples at either the COG Biopathology Center or their treating institution are excluded.