Peripheral T-cell lymphomas (PTCLs) comprise a heterogeneous group of neoplasms that are derived from post-thymic lymphoid cells at different stages of differentiation with different morphological patterns, phenotypes, and clinical presentations. Although a number of case-control studies on non-Hodgkin lymphoma (NHL) have identified various risk factors for disease, including autoimmune conditions, family history of hematopoietic malignancies, smoking, hepatitis C infection, and host susceptibility, these risk factors largely pertain to B-cell lymphoma subtypes as they comprise well over 90 percent of all NHLs. At present, there are no known epidemiologic risk factors for PTCL or its subtypes. This is largely due to the lack of sample size of PTCL in any one epidemiologic study. The aim of this proposal is to implement a standardized epidemiologic risk factor questionnaire into the on-going T-Cell Project. Briefly, the T-Cell Project is an international consortium of on-going clinical trials on peripheral PTCL. It serves as a prospective collection of patients (greater than 18 years) worldwide with PTCL who are enrolled at participating medical institutions for treatment in a clinical trial. The overall goal of the T-Cell Project is to improve current T-cell subtype classifications and to evaluate different treatment strategies for each T-cell subtype. The specific goal of our proposal is to implement, within the T-Cell Project, a 20-minute standardized epidemiologic questionnaire to allow evaluation of various potential risk factors for T-cell lymphomas. Importantly, there are currently no known epidemiologic risk factors for PTCL. We plan to administer questionnaires to 800 PTCL patients; if successful this collection would be the largest database of PTCLs to date with epidemiologic data. If the questionnaire implementation of assessing epidemiological risk factors for PTCL among patients in the T-Cell Project is found logistically feasible, then descriptive and analytic epidemiologic analyses of the collected data to understand the etiology of PTCL would be pursued at the NCI in collaboration with members of the T-Cell Project. For such analyses, NCI would receive only fully anonymized and de-linked data with no identifiers.