The reversed-phase ion pair high performance liquid chromatographic determination of scandium, tin and aluminum with diammonium stilbene-4,4'-bis(1-azo)-3,4-dihydroxybenzene-2,2'-disulfate as precolumn chelating reagent on Spherex C18 column has been investigated with the detection wavelength of 500 nm. Various parameters such as pH, reagent concentration, ion pair reagents, interference of foreign ions have been studied. The mobile phase was methanol-water (40:60, V/V) containing 20 mmol/L acetate buffer of pH 6.0 and 10 mmol/L sodium dodecyl sulfonate. Three complexes could be completely separated within 17 min. The method has been successfully used for the determination of the three metals in mineral samples, with recoveries of 98%, 101%, 103% respectively, and RSD was less than 3.6%. Beer's Law was obeyed over the concentration range 0.01 mg/L-3.80 mg/L, 0.06 mg/L-4.50 mg/L and 0.04 mg/L-3.40 mg/L respectively. The detection limits were 0.9 microgram/L, 1.0 microgram/L and 1.2 micrograms/L for scandium, tin and aluminum when the ratio of signal to noise was 3. Most of other metals did not interfere with the determination. The present method is sensitive and selective.