The proportion of elderly persons (65 years or older) has increased in most countries during the last few decades, and will increase further in the coming years. Annual age-standardised cancer incidence rates per 100,000 elderly persons (1988 to 1992) were calculated based on data from cancer registries in 51 countries in 5 continents kept by the International Agency for Research on Cancer (IARC) and International Association of Cancer Registries (IACR). The proportions of all cancers among elderly men and women were 61 and 56% respectively. All cancers combined (except nonmelanoma skin cancer) were, based on the standardised rates, almost 7-fold more frequent among elderly men (2158 per 100,000 person-years), and around 4-fold more frequent among elderly women (1192 per 100,000 person-years) than among younger persons (30 to 64 years old). However, large variations exist between different cancer sites. Contrary to the pattern in younger age groups, in which annual cancer rates are almost equally distributed among the 2 genders, elderly men have an almost double cancer incidence rate compared with elderly women. For all major specific cancer sites except testicular cancer, the incidence rate is significantly higher among the elderly than among any groups of younger and middle-aged persons. Among elderly men, cancer of the prostate (451 per 100,000), the lung (449 per 100,000) and the colon (176 per 100,000) make up around half of all diagnosed cancers. Prostate cancer is around 22 times more frequent among elderly men than among younger men. The corresponding most frequent cancers among elderly women, making up 48% of all malignant cancers, are breast (248 per 100,000), colon (133 per 100,000), lung (118 per 100,000) and stomach cancer (75 per 100,000). For most cancers, marked geographical variations in incidence rates are found among the elderly, reflecting socioeconomic differences, particularly between the developing and the developed countries. In contrast with other major causes of death among the elderly, cancer incidence and mortality have not in general declined, indicating that primary prevention (especially cessation of tobacco smoking) remains a most valuable approach to decrease mortality; for most of the major cancers (prostate, colon, breast) the causes remain almost unknown. Thus, research into potential causes is urgently needed for future prevention. Since the mortality rates for female cancer in general are declining, and since the incidence is increasing more steeply than the mortality among the men, the number of living elderly ever diagnosed with a cancer will further increase during the next years. Therefore, it is important to emphasise the increasing need for research into the prevention of cancer and the planning of treatment and care in the elderly.