DNA was extracted from the skeletal remains of seven individuals, six infants and one subadult, excavated from a terp near Wijnaldum, in Friesland (Netherlands). Their ages range from the 2nd to the 9th century AD and they were excavated under clean conditions to facilitate DNA analysis. Mitochondrial DNA was amplified from the extracts and the first hypervariable segment of the control region was sequenced. A comparison between the terp inhabitants and modern Frisian speakers shows that the early medieval Wijnaldum inhabitants resemble modern islander Frisian speakers in having a high level of diversity, while the modern mainland Frisians are not distinguishable from the north-west German populations. The amplification of a fragment of the Y chromosome allowed us to determine the genetic sex of the seven individuals. In the case of the subadult, our result is in agreement with the morphological data. For the six infants, DNA analysis is the only way to obtain this information.