The harbour porpoise abundance in the Baltic Sea has dwindled during the 20^th century for largely unknown reasons. Conventional monitoring methods e.g. aerial or ship-based line transects has failed to provide any reliable information on the current status. A novel technical solution is the PCL, Porpoise Click Logger, which can detect and log the biosonar “clicks” of harbour porpoises. The aim of this thesis is to use a large number of PCLs off the southern coast of Sweden to give more information on the presence and distribution of harbour porpoise in that area. The logistics surrounding the deployment and retrieval of the PCLs was handled by local fishermen. The data analyzed in this thesis constitutes 1164 days of monitoring from a total of 30 PCLs on several locations. Over all, 8 occasions with porpoise detections were found. The results prompt further investigations with refined equipment and with focus on more fixed location of the PCL to be able to monitor the low densities of harbour porpoise present off the coast of Sweden