San Marino is a small independent Republic encircled by Italy, with a population of approximately 20,000. It still maintains an ethnic profile favoured by a tendency to genetic segregation due to endogamy. Since 1908 detailed data have been kept on all deaths among residents also for those dying outside the country. In this study the mortality trends based on crude rates are reported for all neoplasms and for selected sites in the years 1908 to 1980, showing increased rates for all neoplasms and the highest rate for stomach cancer. Age-adjusted death rates were calculated for all neoplasms and for selected sites, by sex, in the years 1966 to 1980. Stomach cancer was the commonest cause of cancer death in San Marino and its age-adjusted death rate was the highest in the world. A sharp increase was also observed for respiratory tract and colorectal cancers in recent years.