Conjugated dopamine occurs in the tissues and fluids of many species, and much of this is thought to occur as dopamine sulfate. This paper describes the development and use of a method utilizing reversed-phase paired-ion high performance liquid chromatography to separate and quantitate each of the two naturally occurring dopamine sulfate isomers. Use of the method permitted demonstration of dopamine-3-0-sulfate in human urine from drug-free control subjects. It was found that this compound accounted for 73.1 +/- 27% of the total daily conjugated dopamine excretion in the four subjects studied.