The use of Reversed-Phase High Performance Liquid Chromatography (RP-HPLC) was investigated for the separation of oligonucleotides. By the gradient elution with the mobile phase of methanol, 0.1 M KH₂PO₄ and 0.02 M MaCl₂, the mixtures could be separated in a 250 mm x 1.6 mm LD. column. The number of tieoretical plates rnd resolution were compared between this technique and Micellar Electrokinetic Capillary Chromatography (MECC). The charged nucleic acid constituents in the RP-HPLC were relatively better separated than in the MECC.