Hi Christian, I believe that the argument "var" has changed name to "weights".
The following lines work for me: ... sigma <- rep(sqrt(.5), nrow(lumley1)) # not nrow= lme1 <- lme(Y1 ~ trt.B + trt.C + trt.D + trt.E, random = ~ 1 | trtpair, data=lumley1, weights = varConstPower(form=~sigma, fixed=list(power=1))) lme2 <- lme(Y2 ~ trt.B + trt.C + trt.D + trt.E, random = ~ 1 | trtpair, data=lumley1), weights = varConstPower(form=~sigma, fixed=list(power=1))) I hope you can now make it work!? Christian ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.