Hi there, I have a question on cross over design. There are 3 treatments, each with 3 dose levels, a total of 27 treatment combinations. Each treatment combination is given to a subject in 1 day. However, we can only keep each subject for 9 days, i.e. each subject can have only take 9 treatment combinations. This looks like a incomplete latin square design. Is there any function in R to create such design? Thanks a lot! Lei Liu Assistant Professor Division of Biostatistics and Epidemiology Department of Public Health Sciences School of Medicine University of Virginia 3181 Hospital West Complex Charlottesville, VA 22908-0717 1-434-982-3364 (o) 1-434-806-8086 (c) 1-434-243-5787 (f) liulei at virginia.edu ll9f at virginia.edu