In this work expression of two rhsA elements, ext-a1 and daORF-a1, was differentially induced using IPTG. RhsA is a member of multigene rhs family and can code for five different open reading frames (ORFs), referred to as genetic elements. The functions of rhsA and the different ORFs it codes are not well understood. We used microarrays to study the effect of over-expression of two rhsA elements, ext-a1 and daORF-a1, on E. coli cells. Keywords: time course Overall design: E. coli cells were harvested from biological replicate cultures at 0 hrs (0 mM IPTG) and at 1.5 and 3.5 hrs (0, 0.1, and 1 mM IPTG) after IPTG induction for RNA extraction and hybridization on Affymetrix arrays. A total of seven different conditions were analysed. Two biological replicates and two technical replicates were performed for each condition (a total of 28 microarray hybridizations).