I just wrote up some code for differencing two .RData files or environments (or one of each). Available from source here: http://www.maths.lancs.ac.uk/~rowlings/R/Ediff/ In its handiest form, running: ediff() will tell you the difference between your working environment and the .RData file that it probably started from. Useful for those 'What have I done here?' moments when you discover an R session in a long-lost terminal window. It can take two arguments which can be paths to files or environments. It tells you which objects are in one or the other or both, and does an identical() check on the ones in both. If anyone maintains a package that this could go in, get in touch. Barry -- blog: http://geospaced.blogspot.com/ web: http://www.maths.lancs.ac.uk/~rowlings web: http://www.rowlingson.com/ twitter: http://twitter.com/geospacedman pics: http://www.flickr.com/photos/spacedman