Main sources of information on the epidemiology of malignant tumors are the statistical data on mortality and incidence and the studies on the distribution of frequencies. The mortality from non-Hodgkin's lymphomas ranges between 0.1 and 6 cases per 100 000 per year. Statistics upon incidence are based on cancer registers of the general population. The figures of incidence range between 1 and 10 cases per 100 000 per year ("Cancer Incidence in Five Continents"). Men are affected with non-Hodgkin's lymphoma twice as frequently as women. Burkitt's lymphoma and the lymphoma of small intestine are particularly interesting, showing a peculiar geographical and age distribution.