Current differences in the level of the total fertility rate (TFR) between Dutch municipalities are smaller than they were in the 1970s and 1980s. Nevertheless, there are still considerable differences. Small municipalities have higher TFRs than large cities. This article aims to answer the question whether these differences will decline further until differences between large and small cities disappear. For that purpose we develop a regression model of regional differences in the TFR including demographic, socioeconomic, and cultural variables. Using the estimation results we decompose differences in fertility between large and small cities into the contribution of differences in levels of the determinants versus differences in the relationships between the determinants and fertility. The results show that differences in cultural variables have a larger effect on differences in the TFR than the demographic and socioeconomic variables. As cultural differences do not tend to change quickly, they will not lead to quick changes in regional differences in the TFR. Demographic differences are not expected to lead to strong changes either, as the two demographic variables (household structure and ethnic structure) have opposite effects. As the effect of the socioeconomic variable is caused by differences in the magnitude of the regression coefficient rather than by differences in the value of this variable, even if differences in this variable disappeared, this would still not lead to convergence of the TFR. Thus the article concludes that differences in the TFR between large and small cities are not likely to diminish quickly.