Hi, Thanks to John Zhang <jzhang@jimmy.harvard.edu>, Xiaochun Li <xiaochun@jimmy.harvard.edu>, and aedin culhane <aedin.culhane@ucd.ie> for their prompt answers to this question: Here is the summary of all the answers: (1). >library(annotate) >library("hgu95av2") >tt <- probesByLL("hgu95av2") Comm: probekByLL is a new function of annotate package. You need to update R to 1.9.0 in order to use it. (2) library(hgu95av2) library(annotate) source("reverseEnv.R") Locus2affy <- reverseEnv(lib="hgu95av2", env=hgu95av2LOCUSID) locusids <- c("3448", "2315") affyids <- multiget(locusids, env=Locus2affy) Comm: This probably works but I haven't tried it out. (3) library("hgu95av2") library(annAffy) lls<-c("2322", "2263", "3606", "3456", "3452", "3669", "54963", "9088","5581", "3433") res<-aafSearchText("hgu95av2", "LocusLink", lls) With one locus ID, this also works aafSearchText("hgu95av2", "LocusLink", "3452") Comm: This works. Thanks again for all your help. Best, Ainong Zhou