Hi, Here is a question I have been asked by email, but I tought it could be of help to others. The question was 'write.table(my.exprset) gives an error message. How can I save the expression values I generated with the function express() in a tab separated file ?'. The answer was: - exprSet objects contain different attributes. Try class?exprSet to know more. - Assuming you are interested in the expression values, try write.table(exprs(my.exprset), file="mydata.txt", sep="\t") Hopin' it helps, Laurent -------------------------------------------------------------- Laurent Gautier CBS, Building 208, DTU PhD. Student D-2800 Lyngby,Denmark tel: +45 45 25 24 85 http://www.cbs.dtu.dk/laurent