Immunoglobulins play a central role in B cell physiology. Cross-linking B cell surface immunoglobulin, the B cell antigen receptor, can lead to various cell fates, ranging from cell death to cell survival. There are a variety of different mechanisms that govern the response to B cell antigen receptor cross-linking. One is the overall magnitude of antigen-receptor cross-linking. Another are various accessory molecules that can modulate the signaling, by changing its amplitude or by routing it down various different signal transduction pathways. Study of these molecules and these signal transduction pathways has given us interesting insight into the cytogenesis of CD5 type B-cells, the presumed normal cell counterpart to chronic lymphocytic leukemia. The session on signal transduction pathways and mechanisms of apoptosis in CLL B-lymphocytes addressed the nature of immunoglobulin expression in chronic lymphocytic leukemia, signal transduction in B lymphocytes, as well as in chronic lymphocytic leukemia, the control of apoptosis by members of the BCL2 family, and the nature of the human immunoglobulin repertoire expressed by B cells of normal adults.