ABSTRACT
Chronic lymphocytic leukemia (CLL) is a rare neoplasm that comprises a substantial pro portion of all leukemia in middle-aged persons and is the most common type among elderly persons in western populations. The major causes are not known nor is there de tailed understanding about how the elusive origin(s) may relate to clinical expression, basic biological mechanisms, or pathogenesis. Nevertheless, a growing body of data exists on demographic patterns, international variation, and etiology as described in earlier re views (1-9). Also, with the advent of rapid developments in molecular biology, informa tion is increasing on the molecular aspects of CLL. This chapter will emphasize more recent epidemiology work, particularly for familial and genetic aspects of CLL.
