A method for the determination of urinary nucleosides with reversed-phase high performance liquid chromatography is described. After nucleosides were extracted from urine on phenyl boronic acid affinity chromatography, the analysis was performed on a column (4.6 mm i.d. x 250 mm, 5 microns) at 22 degrees C using a linear gradient elution comprising 25 mmol/L KH2PO4 solution (pH 4.55) and 60% methanol in water with UV detection at 260 nm. This method was used for the determination of 15 urinary nucleosides of 41 intestinal cancer patients and 52 normal adults. The results showed that the average concentrations of 12 urinary nucleosides from intestinal cancer patients were much higher than those of normal adults with P < 0.001. Using the concentrations of 15 nucleosides as the data vectors, principal component analysis was applied to classify intestinal cancer patients and normal adults and 76% (31/41) of the cancer patients were correctly classified. It is concluded that the method is sensitive, reliable and suitable for basic research and clinical applications to malignant tumours.