Women vote less than men in many parts of the world. Whether this gender gap is due to cultural preferences stemming from traditional gender norms or to structural constraints is hard to answer because preferences and beliefs are endogenous to the socioeconomic and institutional environment. To address this problem, we use the so-called epidemiological approach. This approach exploits the portability of culture as a source of identifcation, by comparing migrants from diferent cultures of origin but living in similar institutional environments. We study the gender patterns in turnout of immigrants and their children in Norway using administrative register data on voter turnout. We fnd that gender traditionalism at country of origin is signifcantly correlated with the gender gap in the frst generation, but has no efect in the second generation. Together, our results suggest that early institutional exposureis important for political assimilation.