* Abbreviations: AAP — : American Academy of Pediatrics SHS — : secondhand smoke Smoking rates in the United States have dropped since the first Surgeon General's report on the health effects of smoking was published in 1964.1 Decades of declining prevalence have slowed, however, with some 19.3% of US adults still smoking,2 and 53.6% of children showing biochemical evidence of exposure to secondhand smoke (SHS).3 It is well known that tobacco use leads to disease,4 and that SHS exposure is also harmful; indeed, there is no known safe level of exposure.5 According to the most recent estimates from the World Health Organization, >600 000 people worldwide die prematurely every year of exposure to SHS.6 Of these deaths attributable to SHS, 28% occur in children.6 This number excludes the millions of children worldwide who experience morbidity from SHS exposure. Although the impact of SHS exposure on the severity of pediatric lung diseases such as asthma and bronchiolitis is well known,5 we are only beginning to understand the long-term effects of SHS exposure on cardiovascular health and the pediatric antecedents of adult heart disease. Data from a study by Geerts et al7 in this issue of Pediatrics document that the harmful effects of SHS are found even earlier than expected, with in … Address correspondence to Susanne E. Tanski, MD, MPH, Department of Pediatrics, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Hinman Box 7925, Lebanon, NH 03756. E-mail: Susanne.E.Tanski{at}hitchcock.org