Dear all, Are there any common methods that deal with artifacts that appear on affymetrix arrays? Some of our HGU133A arrays have 'comet-like' high intensity regions. I've isolated the probes contained within these artifacts and was wondering if a 'mask file' could be created in R and these chips re- integrated back into the original dataset? I'd like to include these chips in functions such as rma and hclust etc. Kind regards, Gareth. Gareth Hughes Bioinformaticist Institute of Medical Genetics, UWCM. Email : hughesgp@cf.ac.uk Tel : 029-2074-4837