The objective of this study to investigate possible candidate susceptibility genes for familial chronic lymphocytic leukemia (CLL) by identifying and recruiting high-risk families. Through our ongoing study of familial aggregation in CLL kindreds (protocol 2003-0498 'Genetic Study of Chronic Lymphocytic Leukemia'), we have identified CLL patients who have one or more living or dead relative(s) affected with CLL or other leukemias or lymphomas. We will also identify patients in high-risk families from referrals from leukemia clinicians and from self-referrals from patients who learn about our study from the ClinicalTrials.gov website. We plan to invite probands (patients diagnosed with CLL) and their family members with other leukemias and lymphomas and a sample of unaffected relatives to participate in a genetic/linkage study. We will obtain demographic and clinical information along with specimens (blood or buccal samples) from all participants. These families will be part of the Genetic Epidemiology of CLL Consortium, a multicenter, multidisciplinary consortium, based at the Mayo Clinic Cancer Center under the direction of Susan Slager, PhD. This is funded from NCI through a subcontract with Mayo Clinic.