The cAMP response element consensus sequence directs the transcription of a wide range of genes. A 24-mer single-stranded cAMP response element decoy oligonucleotide (CDO) has been shown to compete with these sequences for binding transcription factors and therefore interferes with cAMP-induced gene transcription. We have examined the effect of this CDOalone and in combinationwith a range of common chemotherapeutic agents in colorectal cancer cell lines.