Here we have tested the ability of antisense oligonucleotides, annealed downstream of the shift-prone site, UCC UGA, to induce shifting of the ribosome to the +1 reading frame. The directionality of frameshifting (either into the +1 or À1 reading frame) is shown to be dependent upon the position of the duplex region relative to the shift site, and the efficiency of frameshifting is responsive to polyamine levels and enhanced by the inclusion of stimulatory sequences found upstream of the human antizyme +1 programmed frameshift site.