In the last several years, sociologists have expanded their interest in simultaneous equation models beyond recursive systems. (See, for example, Duncan and others, 1971; Gurr and Duvall, 1973; Hawkes, 1975; Hibbs, 1973; Kohn and Schooler, 1973; Waite and Stolzenberg, 1976.) The purpose of this chapter is to present some results of potential use in sociology for nonrecursive models estimated by two-stage least squares (2SLS). Two-stage least-squares estimation is widely employed in the