Hi, there: I am using two microarray datasets (both are on the same platform, U133A). I build a predictive model from one dataset and validate the model on another. My aim is to test my methodology's performance on cross-lab situation. I notice the log2intensity are a little bit different between the two arrays (the two arrays are done in two different labs and happen to have some same clinical class label). I use generic scale function in R to "normalize" them. I am wondering if it is appropriate and if there are other approaches for that. Thanks, -- Weiwei Shi, Ph.D Research Scientist GeneGO, Inc. "Did you always know?" "No, I did not. But I believed..." ---Matrix III