A method is described for the rapid purification of radioactively labeled deoxyribonucleoside triphosphates from their spontaneously emerging hydrolysis products deoxyribonucleoside diphosphate, deoxyribonucleoside monophosphate, and deoxyribonucleoside. The separations which are finished within 3 min or less are carried out on a 0.1 X 5 cm column filled with LiChrosorb-NH2, using isocratic elution with 0.025 M potassium phosphate, pH 6.8, in a high-pressure liquid chromatograph at room temperature and a flow rate of 30 ml-h-1 (flow velocity 63.7 cm-min-1).