Oral cancer is considered widely to be a form of cancer whose etiology is well understood and which is becoming relatively rare in developed countries. There have been, however, a series of recent reports indicating that after many years of declining risk, the rates may be rising again in men. To investigate the extent of such changes, national time-series of oral-cancer mortality data available in the World Health Organization's mortality database have been analyzed. Age-period-cohort modeling was used to establish the extent and nature of these changes and to allow comparisons among countries. Nineteen out of 24 national datasets demonstrate a similar pattern of recent increasing cohort-effects for oral cancer in men. The largest increases have occurred in countries of central and eastern Europe where rates have increased by a factor of from three to 10 within a generation. The cohort-based nature of the changes observed in men suggest that there will be a continuing increase in the absolute numbers of cases of oral cancer to be treated in the coming decades.