9321117 Schott Scientists have collegial circles that influence their research. This dissertation will examine how these circles differ between men and women scientists and how the circles differ between the United States and other countries. Scientists have been surveyed in a dozen other countries but at only one U.S. university, where the number of women scientists is too small to enable inference. This grant will support interviews with 80 or more scientists at four other U.S. universities. Preliminary analyses suggest that gender does affect the composition of scientists' circles of colleagues. Notably, at least for scientists in other countries, there is a tendency for same-sex selection. The dissertation will contribute to the understanding of how gender affects informal communication and organization in science and how national contexts shape these gender effects. ***