Hi. I only know how to go from Affymetrix IDs to genbank and unigene, but you may figure it out for your stuff from here. genes<-c("209795_at","208442_s_at") unigene<-multiget(genes,env=hgu133aUNIGENE) genbank<-multiget(genes,env=hgu133aACCNUM) Note there are web tools available as follows if you are really stuck: http://discover.nci.nih.gov/matchminer/html/MatchMinerLookup.jsp http://genome-www5.stanford.edu/cgi-bin/source/sourceBatchSearch Regards Anthony -- ______________________________________________ Anthony Bosco - PhD Student Institute for Child Health Research (Company Limited by Guarantee ACN 009 278 755) Subiaco, Western Australia, 6008 Ph 61 8 9489 , Fax 61 8 9489 7700 email anthonyb@ichr.uwa.edu.au