In March/April 2013 aerial surveys to estimate the abundance of Harbour porpoises Phocoena phocoena on the Dutch Continental Shelf were conducted. These surveys were conducted along predetermined track lines using distance sampling methods in four areas: A “Dogger Bank”, B “Offshore”, C “Frisian Front” & D “Delta”. Between 18 March and 22 April the entire Dutch Continental Shelf (DCS) was surveyed. In total, 197 sightings of 223 individual Harbour Porpoises were collected. Porpoise densities varied between 0.47-1.44 animals/km² in the areas A-D. The overall density on the entire Dutch Continental Shelf was 1.07 animals/km². Harbour Porpoises were widely distributed in March with higher densities in area D “Delta”. In the northern part of the DSC the distribution seemed more patchy, with lower densities in the northern part of area B “Offshore” and in area A “Dogger Bank”.