BACKGROUND While women's participation in higher education has caught up with and surpassed that of men, large gender differences persist in the choice of field of study. To date, we know little about the mechanisms that explain the link between fertility and study disciplines for both men and women. OBJECTIVE To study gender differences in the effect on fertility of earnings potential and gender composition in study disciplines. METHODS We used European Labor Force Survey (EU-LFS) data and OLS models to estimate earnings potential. Next, we linked these estimates to the Generations and Gender Surveys (GGS) of six countries and applied piecewise linear hazard models to analyze the transition to first and second births jointly. RESULTS We found heterogeneity across countries, but within countries the mechanisms tend to be similar for both men and women. CONCLUSIONS This study suggests that the drivers of men's and women's family behavior may be more similar than is often expected. Societal changes that have occurred in the last three decades may lead to a stronger role for men in fertility decision-making, which may remain unnoticed if we continue to focus only on women. Trimarchi & Van Bavel: Gender differences and similarities in the educational gradient in fertility 382 http://www.demographic-research.org CONTRIBUTION This study expands our knowledge of the relationship between men's education and fertility. It also broadens our understanding of the effect of the field of study on the fertility of both men and women by considering two characteristics of the study discipline: earnings potential and gender composition. http://www.demographic-research.org 2.1 Level of education Microeconomic theories predict that education and fertility have opposite associations for men and women (Cigno and Ermisch 1989; Becker 1991; Gustafsson 2001). Following the male-breadwinner model, the price effect is more characteristic of the relationship between education and fertility among women, since childbearing leads to a reduction of time spent in the paid labor market. The income effect-i.e., higher i n c o m e m a k i n g i t p o s s i b l e t o a f f o r d t h e m o n e t a r y c o s t s o f h a v i n g c h i l d r e npredominates among men, since they are supposed to be the main breadwinners. A family model that is built on the specialization and gender division of labor presupposes compensatory roles for housework and paid work between partners, which is why opposite effects of education on fertility are expected for men and women. Scholars have also highlighted mechanisms that are not necessarily specific to men or women. The income effect, usually considered positive, may turn null or even negative. This is because highly educated parents may want to invest more in their children and thus perceive raising an additional child as too expensive. However, highly educated people tend to have more resources (e.g., bigger social networks, financial means to outsource childcare and housework) and skills that can lower the opportun...