Hi A rather odd request, but I am giving a presentation next week on microarrays, and I need some bad data sets which demonstrate the kinds of systematic errors that can be introduced during microarray experiments. I seem to remember a presentation at one of the MGED meetings about some nice cyclical gene expression behaviour which was eventually put down to two different experimenters carrying out the work.... If anyone could point me in the direction of images, presentations and/or data that would very much be appreciated! Thanks Mick