The stone marten (Martes foina) lives in almost all hunting grounds in Croatia and has a large and stable population. This study covered three hunting grounds in northwest Croatia. Twenty-six skulls of the stone marten were collected during a period of five years (2010-2015). Each stone marten was determined with regard to its sex and weight. Sixteen measures were taken from the skulls using a caliper, which were then statistically processed in IBM SPSS Statistics Program, Version 22. From the received data we concluded that sexual dimorphism is weekly pronounced and it is difficult to determine the sex of a stone marten only by its skull. The skulls of males are a little larger than those of females and they are larger in weight. To get more precise differentiation between sexes using craniometric measurements it is necessary to determine the age of the marten first. Statistically significant differences between males and females can be seen from the following measurements: skull height between M1 (SHM), total length of the skull (TL), condylobasal length (CBL), braincase length (BL) and the distance between upper P4 (DPM). Craniometric measures of the stone martens in northwest Croatia are larger than of those in the rest of Europe, with the exception of the stone marten population in the Alps and the Ural Mountains.