The study of the Jak-Stat signaling pathway has now reached an extremely sophisticated level. Nevertheless, significant new insights continue to rapidly emerge involving either novel pathway components or novel actions of known pathway components that have profound influences on signaling through both the Jak-Stat pathway as well as other signaling pathways. Recent work has also shown that Jak and Stats are evolutionarily conserved signaling molecules that regulate a diverse group of fundamental processes ranging from stem cell renewal and embryogenesis to organogenesis and development of hematopoietic and lymphoid ceils. Furthermore their roles in preventing or promoting infectious, malignant and autoimmune diseases have now become areas of intense study and exciting new findings are being made in these areas that have wide applicability to several fields of biology. The goals of this meeting are as follows: (1) Identify novel interactions between members of the Jak-Stat pathway not only with one another but also with receptors and components of other signal transduction pathways with special emphasis on positive and negative acting mechanisms that regulate Jak-Stat pathway signaling; (2) Define the roles of the Jak-Stat pathway and its components in development of primitive and higher organisms with special emphasis being placed on model genetic organisms and on the hematopoietic and immune systems; and (3) Discuss the various protective versus disease-promoting effects of the Jak-Stat signaling pathway in infectious and neoplastic diseases.