Hi Sam, Setting a reference category is equivalent to omitting a category as an independent variable. If you put in dem, rep, and ind id as independent variable, then what's the substantive interpretation when you set all three variables = 0? By omitting a variable (say ind), then you only include dem and rep and so when you set them both equal zero, then the interpretation is that the "person" is an ind. So in running the regression, if you already have the dummies as variables, just leave out which one(s) are the reference category from your regression. If you have one variable for party id, which takes on values of dem, rep, and ind, then you can do it by doing as.factor(), which splits the variable into dummy variables and automatically leaves one out (unfortunately R chooses which one to leave out, usually the lowest one if they are ordinally ranked). As for getting close to the estimates, you should get as close as you can and try to figure out why you can't get exact estimates if possible. 2009/3/21 Sam Barrows <sbarrows at fas.harvard.edu> -- Patrick Lam Department of Government and Institute for Quantitative Social Science, Harvard University http://www.people.fas.harvard.edu/~plam