A world-wide increase in diabetic deaths and a varying rate of increase between one country and another over the past hundred years has long been recognised. During the nineteenth century, the incidence of diabetes was low in Ireland as measured by mortality. Nevertheless, the rising trend found elsewhere was also apparent in Ireland. Recorded deaths were 0.22/100,000 of the population in 1840, rising to 13.2 by 1972. Most of the increase occurred between the 1880s and 1911, but only 15% of this can be accounted for by an ageing population. It is, therefore, necessary to seek other explanations. During the period, sugar and fat consumption in Ireland rose sharply. It has not been possible precisely to relate dietary causes to the incidence of diabetes, but the Irish experience suggests that such a link may exist.