This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The primary objective of this companion study is to determine neuropsychological function among children treated with either high-dose or lower dose methotrexate during participation in a COG treatment trial (AALL0232-IRB4111 or AALL0434-IRB4080).