Chemical shifts of the thallium nuclear resonance have been measured in solutions of thallous hydroxide, fluoride, acetate, formate, nitrate, and perchlorate of varying concentrations and in the presence of added substances. At low concentrations the chemical shift varies non-linearly with concentration of anion and can be correlated with the formation of ion-pairs. In stronger solutions the variation of chemical shift becomes linear, and is attributed to interactions between the ion-pairs and the added substances.