An increasing incidence of non-Hodgkin's lymphoma (NHL) has been reported in several areas of the world and often correlated with the occurrence of AIDS-related lymphomas. A registry specialised in haematopoietic malignancies enabled us to report detailed time trends in the incidence of NHL over the period 1980-89. There was an overall significant increase in incidence of + 10.9% per year (P < 0.001). Such a trend was observed both in men and in women (+ 11.2% and + 10.5%, respectively) and in all age groups. It was slightly more marked in the case of high-grade tumours than for low- or intermediate-grade tumours (+ 20.0%, + 12.6% and + 12.6% respectively) and in rural than in urban areas (+ 19.6% and + 8.1% respectively). In this series, only one case was associated with an HIV infection. These data indicate that, although a significant increase in NHL incidence related to the AIDS epidemic might be expected in the near future, there is an independent dramatic trend which started earlier than the AIDS problem and the causes of which should be investigated.