Dear All: I encountered this several times, could someone point out where the problem is? I don't think it is the memory restriction or something... I have 345 MAS5 results formated as: probeset_id, expression_value, PA_call in 345 text file. I tried to combine them into one single file, but only retain one probeset_ID column. This is my commend: Files<-list.files(pattern=".txt$"); Count<-0; for(i in files) {x<-read.table(i, header=TRUE,sep="\t"); assign(print(i, quote=FALSE),x);if(count==0){combined<-x;rm(x);count<-count+1;} else {combined<-cbind(combined,x[,2:3]);rm(x);count<-count+1;}} After processing over 200 files, the program crashes. Is there a better way to get it done? And, for this large dataset, if I don't want to use RMA -- which is easier to get using justrma, I am stuck here... Thanks Hao