In order to evaluate the antisense effects in biological systems, the interaction of antisense molecules with biological substances such as DNAs and human serum proteins was studied by fluorescence depolarization spectroscopy.When an antisense oligonucleotide anchoring fluorescence (F-AS) was mixed with DNAs or proteins, the anisotropy value changed, indicating that antisense oligonucleotides appreciably interact with DNAs and serum proteins, and that such interaction may play important roles on antisense gene regulation.