The effect of temperature on selectivity in RPLC method development has been evaluated on polybutadiene-coated zirconia. We find that the influence of temperature on selectivity depends strongly on solute type. For solutes of similar structure such as polyaromatic hydrocarbons, temperature has almost no effect on selectivity; however, for solutes with very different functional groups such as chlorophenols, temperature changes did significantly affect selectivity. We feel that simple mixtures with one dominant retention mechanism-e.g., solvophobic retention-will not be helped appreciably by adjusting temperature. However, in complex mixtures with polar and ionizable solutes, optimization by varying the temperature may well be fruitful.