I have the following problem. I am trying to read an affy chip using BioC, the chip is the 10K snp Chip V2. I can't seem to find any methods (in the documentation) that will tell me what quartet offsets are for each probe quartet. i.e. I think I can find the values of the probes for each Affy Probe ID but what I need to know is what base is being used on the mismatched alleles and where it is, in terms of the offset. Any help will be appreciated. R-S -- Dr. Raoul-Sam Daruwala NYU/Courant Bioinformatics Group 715 Broadway, Rm 1011 New York, NY 10003 e-mail: raoul [at] cs.nyu.edu Tel: 212 998 3340 (Office/VM)