Summary. Hepatitis B virus (HBV) infection is endemic in Greenland with 5-10% of the population being HBsAg-positive (chronic carriers). Surprisingly, despite of the high prevalence of HBV infection, acute and chronic hepatitis B, liver cirrhosis and primary hepatocellular carcinoma appear much less frequently than expected. The reasons for the low frequencies are unknown, but as a consequence implementation of a childhood HBV vaccination programme, though debated for years, has never been instituted. We describe an outbreak of hepatitis D (HDV) infection among children in a hepatitis B hyper-endemic settlement of 133 inhabitants on the west coast of Greenland. In 2006 a total of 27% of the inhabitants were HBsAg-positive (chronic carriers) and 83% were HBcAb-positive (previously exposed). Forty-six percent of the HBsAg-positive persons were below 20 years of age. On follow-up 1 year later a total of 68% of the HBsAg-positive persons were HDV-IgG positive. Five children, who were HBsAg-positive in 2006, had HDV-seroconverted from 2006 to 2007, indicating a HDV-super-infection. Most of the HDV-IgG positive children had markedly elevated liver enzymes. In the multivariate analysis, among the HBV and HDV markers, presence of HDV-IgG was most strongly associated with elevation of liver enzymes. In conclusion, the HBV-HDV super-infection and presumed HDV outbreak in this settlement challenges the notion that HBV infection may not be as harmless in Greenland as previously anticipated. The findings strongly suggest that HBV vaccination should be included in the child-immunization program in Greenland.