Add my name to those who think this is a good change. As someone who works daily with medical research data, the number of times I have been caugth by failure of statements like ?? as.Date(ifelse( is.na(prog.dt), lastfu.dt, prog.dt) is a large annoyance.??? Replace ifelse by any number of selection processes for choosing among ending dates. Terry T. -- Terry M Therneau, PhD Department of Quantitative Health Sciences Mayo Clinic therneau at mayo.edu "TERR-ree THUR-noh" [[alternative HTML version deleted]]