To reinforce antisense effects, we focused on the photo-cross-linking ability of psoralen derivatives and examined the applicability of the photodynamic antisense therapy to cancer cells using psoralen-conjugated oligo(nucleosides phosphorothioate)s (Ps-S-Oligo). The regulatory effects of Ps-S-Oligos on the proliferation of cervical carcinoma were evaluated. The inhibitory effects were found to be significant (IC50=16 nM) without any drug delivery systems, and it was also found that the mechanism was associated with the p53 induced apoptosis. This result suggests that the photodynamic antisense therapy will be a promising concept for the cancer therapy.