To compare US population prevalence estimates for myopia in 1971-1972 and 1999-2004. The 1971-1972 National Health and Nutrition Examination Survey provided the earliest nationally representative estimates for US myopia prevalence; myopia was diagnosed by an algorithm using either lensometry, pinhole visual acuity, and presenting visual acuity (for presenting visual acuity > or =20/40) or retinoscopy (for presenting visual acuity -2.0 diopters [D]: 17.5% vs 13.4%, respectively [P -7.9 D: 22.4% vs 11.4%, respectively [P < .001]; < or =-7.9 D: 1.6% vs 0.2%, respectively [P < .001]). When using similar methods for each period, the prevalence of myopia in the United States appears to be substantially higher in 1999-2004 than 30 years earlier. Identifying modifiable risk factors for myopia could lead to the development of cost-effective interventional strategies.