Comparison With Previously Published Data. We compared our findings with those of Boverhof and co-workers by performing a gene-by-gene comparison. Responsive genes were identified in our dataset as those having padjusted < 0.05. A) First, we looked at the 32 genes that responded to TCDD in both species in the Boverhof et al. study and assessed their response in our dataset. Four genes could not be mapped to homologs on arrays, while 57% (16/28) genes responded to TCDD in one or two species in our study. We then repeated this analysis looking at the rat-specific (B) and mouse-specific (C) genes identified in the Boverhof study. In total 24 of the 185 rat-specific genes and 31 of the 225 mouse-specific genes could not be mapped to the 8,125 ortholog pairs present on our oligonucleotide arrays. Next we mapped the specific fold-changes observed in the two studies for both species (D). Highly similar patterns were observed for both mouse (Spearman's rho = 0.83, p = 4.4 × 10-8) and rat (Spearman's rho = 0.88, p = 1.06 × 10-9).