Abstract: The invention relates to the identification and use of gene expression profiles with clinical relevance to the treatment of cellular proliferative disorders, especially those mediated by aberrant Notch signaling using a Notch signaling inhibitor. In particular, the invention provides the identities of genes, whose individual or cumulative expression patterns may be useful in various assays. The gene expression profiles, whether embodied in nucleic acid expression, protein expression, or other expression formats, may be used to select subjects afflicted with a Notch mediated cancer who will likely respond to treatment with a gamma-secretase inhibitor or another Notch inhibiting agent. The same markers may be used in the classification of patients being treated with other Notch inhibitors. The methods may further comprise providing diagnostic, prognostic, or predictive information based on the classifying step. The methods may further comprise selecting a treatment based on the classifying step.