A method was developed for the high-performance liquid chromatographic determination of dithiocarbamates (DTCs), after conversion of zinc dithiocarbamates into the corresponding cobalt(III) complexes. When shaking a chloroform-acetone extract from a rubber sample with cobalt(II) chloride, mixed-ligand cobalt(III) complexes were often formed because of the coexistence of more than two kinds of zinc dithiocarbamates in the rubber sample. The chromatograms were so complicated that DTCs could not easily be determined in the usual manner. However, it was possible to identify and to quantify DTCs by comparing retention times and relative intensities of the multiple peaks of the cobalt(III) complexes obtained from standard mixtures of zinc dithiocarbamates.