Objectives: In The Netherlands, part of the population experienced food restriction and severe famine during World War II. The purpose of this study was to study the effects of severe undernutrition during adolescence on the risk of breast cancer later in life. Methods: We examined the hypothesis in the Netherlands Cohort Study on diet and cancer (NLCS), among 62,573 women aged 55-69 years. Baseline information on diet and other risk factors was collected with a questionnaire in 1986. Information was collected on residence in the Hunger winter (1944-1945) and War years (1940-1944) and fathers' employment status in 1932-1940 as indicators of exposure. After 6.3 years of follow-up, 1009 incident breast cases were available for analysis. Results: In multivariate case-cohort analysis, residents of the western part of the country in 1944-1945 had an increased breast cancer risk (western city RR = 1.1, 95% CI: 0.9-1.4, western rural area RR = 1.5, 95% CI: 1.1-1.9). For the War years (1940-1944) we found no association between breast cancer risk and urban vs. rural residence. Women whose fathers were unemployed during the Depression years (1932-1940) had a non-significant decrease in breast cancer risk (RR = 0.9, 95% CI: 0.7-1.2). Exposure to energy restriction during the adolescent growth spurt or during the period between menarche and birth of the first child did not change the RRs substantially. Conclusions: We found no clear evidence in this study for the hypothesis that energy restriction in adolescence leads to a decreased breast cancer risk.