The cultural and linguistic diversity of the U.S. population presents challenges to the design and implementation of population-based surveys that serve to inform public policies. Information derived from such surveys may be less than representative if groups with limited or no English language skills are not included. The California Health Interview Survey (CHIS), first administered in 2001, is a population-based health survey of more than 55,000 California households. This article describes the process that the designers of CHIS 2001 underwent in culturally adapting the survey and translating it into an unprecedented number of languages: Spanish, Chinese, Vietnamese, Korean, and Khmer. The multiethnic and multilingual CHIS 2001 illustrates the importance of cultural and linguistic adaptation in raising the quality of population-based surveys, especially when the populations they intend to represent are as diverse as California's.