We have analyzed the response of a number of human cell lines to treatment with antisense oligodeoxynucleotides (ODNs) directed against RNA polymerase II, replication protein A, and Ha-ras. ODN-delivery to the cells was liposome-mediated or via electroporation, which resulted in di erent intracellular locations of the ODNs. The ODN-mediated target mRNA reduction varied consider-ably between the cell lines.