Many women do not work in science, technology, engineering, and mathematics (STEM) occupations even though they have degrees in these subjects. To shed light on this problem, we use information from the German Graduate Panel and show a significant gender gap among STEM graduates working in degree-related occupations after graduation. Therefore, we focus on university graduates' transition into the labour market and include male and female non-STEM and STEM graduates. We find that male STEM graduates are more likely to work in a degree-related field than other men. A gender gap in degree-related work in STEM occupations shows that this is not the case for women. Separating STEM into engineering and computer science (EngComp) and mathematics and natural sciences (MatNat) shows that EngComp graduates are the main driver of the STEM effects. The estimations remain robust to a comprehensive set of individual background information. Moreover, bearing children before graduation or at the beginning of one's professional career does not explain the lower entry behaviour of female EngComp graduates. Possible channels for why women with an EngComp degree are not as likely as men to start their professional life in an EngComp occupation are discussed.