A product’s physical appearance is difficult to quantify, and the impact of product appearance on demand has rarely been studied using market data. The authors adopt a recently developed morphing technique to measure a product’s aesthetic design and investigate its effect on consumer preference. Drawing upon categorization theory, the authors consider the effects of three dimensions of aesthetic design—segment prototypicality (SP), brand consistency (BC), and cross-segment mimicry (CSM)—and their moderating effects on marketing mix effectiveness in a unified framework. The empirical analysis uses a unique, large data set consisting of 202 car models from 33 brands sold in the United States from 2003 to 2010. The authors find that consumer preference peaks at moderate levels of SP and BC and that economy-segment products benefit from CSM of luxury products. Moreover, SP intensifies price sensitivity, and BC muffles price sensitivity while increasing advertising effectiveness. Two what-if studies illustrate how managers can use the empirical model to evaluate alternative aesthetic design choices.