Hi, On the limma usersguide I found the example: FileName Cy3 Cy5 File1 wt1 mu1 File2 wt1 mu1 File3 wt2 mu2 File4 wt2 mu2 where two wild-type and two mice from the same mutant strain are compared using two arrays for each pair of mice. > biolrep <- c(1, 1, 2, 2) > corfit <- duplicateCorrelation(MA, ndups = 1, block = biolrep) > fit <- lmFit(MA, block = biolrep, cor = corfit$consensus) > fit <- eBayes(fit) > topTable(fit, adjust = "BH") I have something like this, but, in my case, I have: FileName Cy3 Cy5 File1 pra1 banha1 File2 pra1 banha1 File3 pra2 banha2 File4 pra3 banha3 banha is my reference and pra is my tester. Only the two first is technical replicates. The others two are biological replicates. How I could dealing a design for my situation? Thank you very much. -- Marcelo Luiz de Laia Universidade do Estado de Santa Catarina UDESC - www.cav.udesc.br Lages - SC - Brazil Linux user number 487797