The trends in liver cancer incidence and mortality were investigated by gender in Japan, Norway, Singapore, Spain, Sweden, the UK and the USA. Cancer Incidence in Five Continents, Vols I-VI, were the principal source of the analysis of age specific incidence rates by sex; additional incidence information was obtained from the published data of the Connecticut Tumor Registry and the Surveillance, Epidemiology and End Results Program in the USA. Mortality rates were calculated using the World Health Organization database. The trends observed were generally weak. Increasing occurrence of primary liver cancer was noted in Japan and the Nordic countries, although the rates seemed to be stabilizing or even decreasing in the most recent data from Sweden. By contrast, decreasing trends were apparent in Spain and Singapore. Changes in the rates appeared to be more evident or somewhat stronger for males than for females. Some biological explanations were offered to account for these trends. However, the dominant determinants of the apparent changes in the incidence and mortality of primary liver cancer were felt to be related to classification and coding revisions as well as to variations over time in diagnostic and certification practices.