Increasingly, firms allow consumers to mass customize their products. In this study, the authors investigate consumers' evaluations of different mass customization configurations when they are asked to mass customize a product. For example, mass customization configurations may differ in the number of modules that can be mass customized. In the context of mass customization of personal computers, the authors find that mass customization configuration affects the product utility that consumers can achieve in mass customization as well as their perception of mass customization complexity. In turn, product utility and complexity affect the utility that consumers derive from using a certain mass customization configuration. More specifically, product utility has a positive effect and complexity has a negative effect on mass customization utility. The effect of complexity is direct as well as indirect because complexity also lowers product utility. The authors also find that consumers with high levels of product expertise consider mass customization configurations less complex than do consumers with low levels of product expertise and that for more-expert consumers, complexity has a less-negative impact on product utility. The study has important managerial implications for how companies can design their mass customization configuration to increase utility and decrease complexity.