This is a summer research conference to be held June 26 through July 1, 1999 in Saxtons River, Vermont under the auspices of the Federation of American Societies for Experimental Biology. The conference will focus on the structure and function of membrane receptors that play critical roles in the modulation of immune responses. These receptors include such important members as the antigen receptors of T and B lymphocytes and cytokine receptors. A special emphasis will be given to the rapidly moving field of inhibitory receptors involved in negative signaling pathways. There will be two keynote lectures to be given by Dr. Don Wiley, a leader in the structural biology of immunoreceptors, and Dr. William Paul, a leader in cytokine biology. In addition there will be eight scientific sessions on specific topics with invited speakers, and one session devoted to the discussion of selected posters submitted to the conference. The themes of the scientific sessions are (1) the T cell receptor, (2) the B cell receptor, (3) Fc receptors, (4) inhibitory receptors, (5) accessory and adapter molecules, (6 & 7) kinases, phosphatases and other signaling elements, and (8) cytokines and their receptors.