A liquid chromatographic method that can separate each of the monoamino analogues of dideoxyadenosine and 9-(dideoxy-beta-D-lyxo-pentofuranosyl)adenine from their main degradation product, adenine, is described. The influence of the pH of the mobile phase, the type and concentration of the organic modifier and the concentration of the silanol masking agent and the buffer have been investigated. Several reversed phases were examined. Samples were finally analyzed on a 10 mum Spherisorb ODS1 column (250 mm x 4.6 mm I.D.) using acetonitrile - 0.2 M potassium phosphate buffer pH 6.0-0.2 M tetramethylammonium phosphate pH 6.0-water (5 :5: 0.5: 89.5, v/v) as the mobile phase. The interactions between the solute and the stationary phase are discussed in view of the basic properties of the compounds under study.