Disclosed are double-stranded antisense nucleic acid complexes that can efficiently alter the processing of RNA in a cell via an antisense effect, and methods for using the same. One method comprises contacting with the cell a double-stranded nucleic acid complex comprising: a first nucleic acid strand annealed to a second nucleic acid strand, wherein: the first nucleic acid strand comprises (i) nucleotides independently selected from natural DNA nucleotides, modified DNA nucleotides, and nucleotide analogs, (ii) no regions that have 4 or more consecutive natural DNA nucleotides, (iii) the total number of natural DNA nucleotides, modified DNA nucleotides, and nucleotide analogs in the first nucleic acid strand is from 8 to 100, and (iv) the first nucleic acid strand is capable of hybridizing to RNA inside of the cell and the second nucleic acid strand comprises nucleotides independently selected from natural RNA nucleotides, modified RNA nucleotides, and nucleotide analogs.
