The effects of various inorganic cations and anions on the chromatographic behaviour of insulin and its derivatives have been investigated. It was shown that on an octadecylsilica column at a given eluent composition the retention of insulins depends primarily on the nature of the anions. The cations have a secondary effect, depending on their size and coordination ability. The mechanism of the effect of the ions is complex. It includes the formation of ion pairs, their influence on dissociation processes, a silanophilic effect, coordination processes and changes in the structures of the insulins.