Dear R-Help, I am using R2.3.0, nlme library on Windows XP. I created a grouped data object with y, subject, group and time variables. I can plot the data using plot.nfnGroupedData(form=y~time|subject,outer=~group) This gives me individual curves (connected points) for each subject in separate panels for each group. I would also like to add to the plot a curve with the mean y at each time point for each group. how can I do that? Thanks -- Osman O. Al-Radi, MD, MSc, FRCSC Fellow, Cardiovascular Surgery The Hospital for Sick Children University of Toronto, Canada [[alternative HTML version deleted]]