Hi Bobby, Bobby Prill <rprill at jhu.edu> writes: > R Version 2.2.1 (2005-12-20 r36812) You need to upgrade to a more recent version of R (yours is quite old in R-years). Once you have upgraded to R-2.4.1, you should be able to install Rgraphviz: source("http://bioconductor.org/biocLite.R") biocLite("Rgraphviz") + seth