In R 2.11.0, the following code that appends data using gzfile in 'ab' mode doesn't work anymore (it worked in the previous versions): con <- gzfile('myfile.gz', open='wb') write.table(c(1,2,3), file=con) close(con) con <- gzfile('myfile.gz', open='ab') write.table(c(4,5), file=con) close(con) The file contains only entries from the first call (1,2,3). I have tried it on Windows as well as on Mac OS platforms - the same behavior. Is there anything I'm doing wrong? Thanks, Hana Sevcikova