John R. Lott and David B. Mustard (1997} provide evidence that enactment of concealed handgun ('right-to-carry') laws deters violent crime and induces substitution into property crime. A critique by Dan A. Black and Daniel S. Nagin (1998) questions the particular model specification used in the empirical analysis. In this paper, the authors estimate the 'model uncertainty' surrounding the model specified by Lott and Mustard using an extreme bound analysis (Edward Leamer 1983). They find that the deterrence results are robust enough to make them difficult to dismiss as unfounded, particularly those findings about the change in violent crime trends. The substitution effects are not robust with respect to different model specifications. Copyright 1998 by Oxford University Press.