Antisense oligonucleotides offer the promise of therapeutic effect with few toxic effects, by virtue of their high selectivity. Preclinical studies have provided evidence of antisense effects in vitro and in vivo, and phase I clinical trials have demonstrated safety, feasibility and activity of antisense oligonucleotides for the treatment of cancer. This review summarizes the status of development of three anticancer antisense oligonucleotides from ISIS Pharmaceuticals.