Online product ratings have become a major information source for customers, retailers, and manufacturers. Both practitioners and researchers predominantly interpret them as a reflection of product quality. We argue that they in fact represent the customer’s satisfaction with the product. Accordingly, we present a customer satisfaction model of online product ratings which incorporates the customer’s pre-purchase expectations and actual product performance as determinants of ratings. We validate our model by applying it to two datasets collected at the German website of Amazon.com. The results indicate that both factors have a significant influence on online product ratings, supporting the proposed interpretation of ratings.