This research focuses on a previously unexamined risk associated with the widely used new product development strategy of line extensions. Specifically, it explores consumer reactions when line extensions become too visually similar and examines both short-term and longer term strategies for solving the problem. Examined in the context of consumer durables, specifically, automobiles, the results show that consumers who make categorization mistakes when trying to distinguish between two visually similar product lines have more negative attitudes not only toward the product but also toward the parent brand. The results of Study 1 confirm that providing a design vocabulary that articulates the car's design features is effective in reducing consumer's categorization mistakes. In addition, results of Study 2 indicate that changes to the car's “eyes” (headlights) are more effective than changes to the car's “mouth” (grille) in helping consumers to differentiate among cars in the line.