Background: Despite surging interest in taxation as a policy to address poor food choice, US research directly examining the association of food prices with individual intake is scarce. Methods: This 20-year longitudinal study included 12 123 respondent days from 5115 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Associations between food price, dietary intake, overall energy intake, weight, and homeostatic model assessment insulin resistance (HOMA-IR) scores were assessed using conditional log-log and linear regression models. Results: The real price (inflated to 2006 US dollars) of soda and pizza decreased over time; the price of whole milk increased. A 10% increase in the price of soda or pizza was associated with a -7.12% (95% confidence interval [CI], -63.50 to -10.71) or -11.5% (95% CI, -17.50 to -5.50) change in energy from these foods, respectively. A $1.00 increase in soda price was also associated with lower daily energy intake (-124 [95% CI, -198 to -50] kcal), lower weight (-1.05 [95% CI, -1.80 to -0.31] kg), and lower HOMA-IR score (0.42 [95% CI, -0.60 to -0.23]); similar trends were observed for pizza. A $1.00 increase in the price of both soda and pizza was associated with greater changes in total energy intake (-181.49 [95% CI, -247.79 to -115.18] kcal), body weight (-1.65 [95% CI, -2.34 to 0.96] kg), and HOMA-IR (-0.45 [95% CI, -0.59 to -0.31]). Conclusion: Policies aimed at altering the price of soda or away-from-home pizza may be effective mechanisms to steer US adults toward a more healthful diet and help reduce long-term weight gain or insulin levels over time. ©2010 American Medical Association.