The World Values Survey is the product of an unprecedented collaboration of investigators from five continents. Using this survey, an international "postmaterialism" scale was developed. This scale shows a worldwide trend away from concerns with material well-being toward a postmaterialist value system that emphasizes the free expression of ideas, greater democratization, and the development of more humane societies. I test the assumption that a single latent trait of postmaterialism accounts for the observed response patterns to items that make up the scale. Applying a log-linear Rasch model, I test the assumption that the scale is a consistent cross-national measuring device and find that the scale is not unidimensional. Item bias is identified after controlling for the common stratification variables of gender, education, age, and country.