As part of a research project on medieval trade and maritime transportation in the former Norwegian province of Bohuslän, western Sweden, a dendrochronological analysis of the so-called Mollö cog was undertaken. The wreck, which was first salvaged in 1980, was previously dated by 14 C analysis. Since this provided a nearly 400-year time-span for the building of the vessel, a more precise dating was considered essential. In conjunction with dendrochronological sampling, several features not previously reported were recorded. This paper presents the find, the research history and the results of the dendrochronological investigation. ©