I summarise new facts on hours worked differences across countries and their driving forces. The facts are derived from a comprehensive analysis of micro data sets. First, hours worked are substantially higher in poor than in rich countries. Second, lower hours worked in Europe than in the US can partly be explained by differences in vacation weeks and partly by differences in the demographic structure. Moreover, employment rates tend to be higher and weekly hours worked lower in Western Europe and Scandinavia than in the US, with the opposite being true in Eastern and Southern Europe. Last, among core-aged individuals, married women form the group that exhibits the largest differences in hours worked across countries. International differences in taxation, and especially in the tax treatment of married couples, are an important driver of these differences.