Even though the association between liver cirrhosis and glucose tolerance alterations has been well documented, no data are available on the incidence of this association. In this paper we firstly report the results of a 4-year prospective longitudinal study performed on well-compensated cirrhotic patients with a normal glucose tolerance, in order to evaluate the incidence of glucose tolerance alterations with respect to liver efficiency during the time. The incidence of a diabetic response to a standard OGTT was 4.4% after a 1-year and 21.2% after a 4-year follow-up in stable cirrhotics. These figures are significantly higher than in the general population of our country. This large incidence was even significantly higher in cirrhotics with worsening liver efficiency at the end of the study (35.3%, P < 0.0001). Sex, family history of diabetes, alcoholic aetiology of the cirrhosis, and increment of portal hypertension do not seem to have any significant influence on the frequency of altered glucose tolerance. Therefore, we propose that liver cirrhosis and its worsening play a primary role as diabetogenic risk factors.