On counting the incidence of infectious mononucleosis (MI) in Greenland during the period 1963-80, 82 cases were found. Information about ethnic status was not available. The observed cases were equivalent to 1/10 of the expected incidence based on the Danish MI incidence correlated to the total population in Greenland. Observed cases related to a given expected number of cases based on the non-inborn population in Greenland and the Danish MI incidence showed good correlation. In the period of 1970-79, eight patients with infectious mononucleosis were diagnosed. All were Danes born in Denmark or in Greenland to Danish parents. Infectious mononucleosis is thus a rarely reported illness among Eskimoes in Greenland which implies that the primary Epstein-Barr virus infection takes place in early childhood. The results from a high risk area of nasopharyngeal carcinoma such as Greenland thus correlated with similar observations in a high risk area for Burkitt's lymphoma such as Central-Africa.