Summary.A method has been developed for producing measurable and reproducible coronal colour changes in teethin vitro. Two tecfhniques with different access preparations were assessed for the prevention of dehydration of enamel. Rclative discoloration was also compared in freshly extracted teeth and teeth which had been stored in ethanol. The most reproducible results were obtained with an immersion technique of humidity control and with apical access to the pulp chamber. Freshly extracted teeth or teeth stred in ethanol appeared to be equally suitable for determining the relative staining of the crown compared with the original tooth colour. It is considered that the method could be applied to studies for investigating the discolouring properties of endodontic materials.