Trends in age-specific suicide rates relate to debates about the consequences of population aging and changes in cohort size for social well-being. Easterlin argues that large cohort size increases suicide rates by reducing relative income; Preston claims that suicide rates fall in large cohorts with high levels of political and social power. To integrate these competing arguments, this paper uses aggregate data on 18 high-income nations from 1953 to 1986 to demonstrate that the direction and strength of the relationship between cohort size and suicide depend on (1) age of the cohort, (2) gender, (3) national context, and (4) time period. The results show that large cohort size raises suicide for the young and middle-aged, but reduces it for the elderly. Also, the effects of cohort size prove stronger for men than for women, for nations with less collectivist institutions than for nations with more collectivist institutions, and for the 1950s and 1960s than for the 1970s and 1980s.