Since the second half of the 20th century, the decline in fertility has been a constant in practically all advanced societies. This study increases our understanding of the multidimensional character of this phemomenon, addressing educational and labour market factors, the impact of public policies, the transformation of gender roles and new family configurations. Spain is the object of this in depth analysis because it exhibits behaviour that deviates from other cases of low fertility. Women in Spain postpone motherhood; they face difficulties in balancing family and career; support from the welfare state for families is insufficient and couples doubt if they should have children due to economic and social uncertainties. Spain also has a very high unemployment rate, in particular, among young people, and has seen a spectacular increase in the rates of divorce and cohabitation. The authors analyse the factors that explain the uniqueness of the Spanish case, comparing it not only with the reality in Nordic and Anglo-Saxon countries, but also with Spain’s mediterranean neighbours.