First, thanks for creating such a useful R package. I am a new Zelig (2.8.3) user, but I can already see its time-saving potential. However, I am having some trouble using the bprobit model, and I hope someone can help me. I want to model something like: mu1 = x1 %*% b1 mu2 = x2 %*% b2 rho = f(x3 %*% b3) where mu1 and mu2 are the means of the underlying bivariate probit, and f() is the exp(x)-1/exp(x)+1 transformation. x1, x2 and x3 are vectors of variables, and are all different. The zelig command I am using is z.out <- zelig(list(mu1 = y1~x1, mu2 = y2~x2, rho = ~x3), model="bprobit",data=mydata) Note that x1 is really x11+x12+x13+..., and so forth. My problem is that when I do summary(z.out), I get coefficient estimates for b1 and b2, but only a single intercept estimate for b3. If I change x3 variables, I get the same estimate for b3. It is as though zelig is ignoring all of the covariates I put on rho. I didn't see a reference to this in the list archives, but I'm wondering if this is a known issue. From the documentation, it looks like this should be possible. Thanks in advance, Michael -- Michael Braun Assistant Professor of Marketing MIT Sloan School of Management One Amherst St., E40-169 Cambridge, MA 02142 (617) 253-3436 braunm(a)mit.edu - Zelig Mailing List, served by Harvard-MIT Data Center Send messages: zelig(a)lists.gking.harvard.edu [un]subscribe Options: http://lists.gking.harvard.edu/?info=zelig Zelig program information: http://gking.harvard.edu/zelig/