Anne, you can accomplish your goal by using my Rdsm package, which adds a threads-like capability to R. You can download it from CRAN. Look in particular in the examples/ directory. The file WebProbe.R is pretty much exactly the same usage that you want. Look at Auction.R too. You may also find my UseR! presentation on Rdsm to be helpful, user2010.org/slides/Matloff.pdf You could do the same thing, though less directly and I believe less conveniently, using some of the packages Louis mentioned, as well as bigmemory. Norm Matloff