Background: Women treated with therapeutic chest radiation may develop breast cancer. Purpose: To summarize breast cancer risk and breast cancer surveillance in women after chest radiation for pediatric or young adult cancer. Data Sources: Studies from MEDLINE, EMBASE, the Cochrane Library, and CINAHL (1966 to December 2008). Study Selection: Articles were selected to answer any of 3 questions: What is the incidence and excess risk for breast cancer in women after chest radiation for pediatric or young adult cancer? For these women, are the clinical characteristics of breast cancer and the outcomes after therapy different from those of women with sporadic breast cancer in the general population? What are the potential benefits and harms associated with breast cancer surveillance among women exposed to chest radiation? Data Extraction: Three investigators independently extracted data and assessed study quality. Data Synthesis: Standardized incidence ratios ranged from 13.3 to 55.5; cumulative incidence of breast cancer by age 40 to 45 years ranged from 13% to 20%. Risk for breast cancer increased linearly with chest radiation dose. Available limited evidence suggests that the characteristics of breast cancer in these women and the outcomes after diagnosis are similar to those of women in the general population; mammography can detect breast cancer, although sensitivity is limited. Limitation: The quality of evidence for key questions 2 and 3 is limited by substantial study heterogeneity, variation in study design, and small sample size. Conclusion: Women treated with chest radiation have a substantially elevated risk for breast cancer at a young age, which does not seem to plateau. In this high-risk population, there seems to be a benefit associated with early detection. Further research is required to better define the harms and benefits of lifelong surveillance. © 2010 American College of Physicians.