Agreed. SAS support confirmed there is no option for this.   Since I am only interested in the number of subjects with complete data (sufficient information) to predict Y at a given visit for each treatment group, I am using a simple descriptive frequency (proc sql and/or proc freq) of the count of unique subjects with non-missing data across all the variables included in the mixed model (excluding the outcome/dependent variable).   According to SAS: "PROC MIXED does require non-missing values for the dependent variable for the model estimation. In other words, if an observation has a missing value for Y, it will not be included in the model estimation. However, you might obtain the predicted value for this observation, as long as all the independent variables in the model are non-missing. So you might want to modify how you count the subjects in your program, if the count is for the model estimation purpose."     ... View more