Recent studies have revealed that some RNAs are transcribed from noncoding DNA regions, including pseudogenes, and are functional as riboregulators. We have attempted to assess the gene expression profile throughout the Mycobacterium leprae genome using an array technique. Twelve highly expressed gene regions were identified that show an alteration in expression levels upon infection. Six of these were pseudogenes. Although M. leprae has an exceptional number and proportion of pseudogenes among species, our results suggest that some of the M. leprae pseudogenes are not just 'decayed' genes, but may have a functional role.