The development of new drugs against cancer requires established cell lines. They are needed for in vitro studies to identify candidate drugs and in xenograft models to measure drug efficacy in vivo. Specific criteria need to be fulfilled by cell lines used in the evaluation of potential novel therapeutic agents. It is imperative that they display the features of the particular cancer under investigation. Given the documented heterogeneity of cancers, relevant subtypes need to be represented. In this study, we have examined these aspects for pediatric acute lymphoblastic leukemia. A panel of 13 leukemia cell lines recently established in our laboratory was analyzed. We used cDNA microarrays to define the gene expression profiles and compared the data with immunophenotyping and cytogenetic analyses. The expression profiles obtained showed excellent concordance with corresponding protein levels. Importantly, the panel of lines displayed the critical genetic features identified in clinically important acute lymphoblastic leukemia subtypes in childhood leukemia patients.