Dear list, I have an experiment with 24 arrays. I have 3 factors each with 2 levels and 12 blocks (1,1,2,2,3,3,....,12,12). Each gene is replicated 4 times on each array. I know how to fit blocks as random as explained in the Limma manual (Technical replication I) I know how to account for the replication within arrays. Is it possible to fit random block effect and technical replicates within array at the same in linear model using Limma ? Thanks Peter