Reversed-phase liquid chromatography (RPC-5) was the first chromatographic technique to be successfully applied to DNA restriction fragments. Size-exclusion high-performance liquid chromatography (HPLC) has the advantage of wide variability in buffer conditions but is restricted to an upper size limit at 800 base pairs. Anion-exchange HPLC is most versatile and may best be scaled up for the preparation of milligram amounts of specific DNA fragments. The preparation of the sample before and after chromatography is described. Because several applications of DNA fragments will be complemented by RNA fragments, their preparation and purification is included. Disposable small-scale columns are available for processing many samples. Future medical applications of HPLC of DNA fragments concern medical microbiology, human genetics and forensic medicine.