Many analysts are not taking full advantage of the high speed possibilities of modern LC. Some analytical procedures reported in the literature, and many in regular use in control laboratories, could be achieved in less time without loss in precision. Some factors which affect retention times are discussed and the advantages and disadvantages of employing shorter column lengths and finer packing materials in reversed-phase HPLC are examined. The effect on efficiency of increased flow rates with 10,5 and 3 μm ODS materials is shown. The ability to couple shorter column lengths without loss of efficiency is also demonstrated. This allows a minimum length to be selected that gives adequate resolution. Examples of high speed separations are shown and limitations in ‘state of the art’ HPLC equipment and chromatographic data systems are discussed briefly.