Hi All I am trying to estimate a simultaneous equation model as follows: X = a.Y + b.Z + c.W Y = d.Z + e.W X is a categorical variable (0/1) and Y is a continuous variable. Can I use the tsls (two stage least square) function in the sem package to estimate this? Or, is there any other function that I can use in R? Thanks in advance, Sunil _________________________________________________________________ Helping your favorite cause is as easy as instant messaging. You IM, we give. [[alternative HTML version deleted]]