Hello, I am analyzing a dataset where the response is count data. I have one two-level factor that is repeated within-subjects and additional between-subject variables that are either categorical or continuous. I have previously modeled a comparable dataset (without the within-subjects factor) using glm with family=poisson, but see no way to incorporate repeated measures with the glm function. Here is a small dataset that illustrates the data structure, note that each subject is repeated twice, once for each level of factor "X1": dframe <- data.frame(response=rpois(1:10,2),subjects=sort(rep(c("Tom","Nic","Bil","Jon","Jil"),2)),X1=rep(c("A","B"),5),X2=rep(sapply(1:5,function(x) rnorm(1)),each=2)) Can someone suggest an approach to test for an effect of "X1" and "X2" on "counts"? Best, Jonathan [[alternative HTML version deleted]]