Disodium glycyrrhizinate (DG) was administered at concentrations of 0.15 (maximum tolerated dose), 0.08, 0.04 or 0% in the drinking-water to groups of 50, 70, 60 and 60 male B6C3F1 mice, respectively. Female groups, each consisting of 50 mice, were given DG in the drinking-water at concentrations of 0.3 (maximum tolerated dose), 0.15, 0.08 or 0%. Treatment was continued for 96 wk and the experiment was terminated at wk 110. There was no difference between treated and control groups in tumour incidence, in the latent period before tumours appeared or in the distribution of different types of tumour. Thus the long-term oral administration of DG to mice did not yield any evidence of chronic toxicity or tumorigenicity.