 1. Patients with a diagnosis of previously untreated aggressive non-Hodgkins lymphoma, including patients with mantle cell lymphoma, who will be or are receiving treatment with R-HyperCVAD and R-Ara-CMTX. Patients in whom Rituximab is not used, due to contraindication, will be eligible. Patients whose therapy was switched to RHyper-CVAD after initial treatment with RCHOP, because of aggressive disease will also be eligible for the study. 