Traditional measures of proximity all share three common weaknesses: (1) they are based on ratio-level measurement of physical distance that may not correspond to "psychological distance;" (2) they measure distance as a fixed rather than variable quantity; and (3) they measure distance between pairs of individuals rather than larger groups of people. A conceptualization of proximity which attempts to deal with these problems for use in large organizations is developed in this paper. Proximity is defined as the probability of people being in the same location at the same point in time, that is, as an opportunity for face-to-face communication made possible by time and space. It is operationalized as a mean joint probability among all people in the organization. A computer program, PROXVAL, which was developed to calculate the required quantities, is described. Initial attempts at pilot testing the procedure are reported. (Author)