This study analyzed the contribution of selected causes of death to rectangularization of the survival curve of Dutch men and women above age 60 in the 1980s, and determined why rectangularization took place in the 1980s but not in the 1970s. The contribution of causes of death was determined by means of a decomposition analysis, using mortality data by underlying cause of death, sex, and age from Statistics Netherlands. Our results show that mortality reductions from ischemic heart disease, cerebrovascular diseases, and lung cancer (men only) and mortality increases from chronic obstructive pulmonary diseases (men only) and mental disorders (women) contributed to rectangularization in the 1980s. Comparison with the 1970s, in addition, demonstrated that in particular changes in mortality at advanced ages (i.e., smaller mortality reductions and mortality increases) were responsible for the reversal from a decreasingly rectangular shape of the survival curve in the 1970s curve to rectangularization in the 1980s. The combination of increased survival to advanced ages and reduced survival at advanced ages explains why rectangularization of the survival curve took place recently in The Netherlands.