Patellofemoral disorders represent a large portion of the average orthopedist's practice. Despite the improvements in patellofemoral radiographs and arthroscopic diagnostic techniques, these disorders are too frequently misunderstood and frustrating to treat. This report proposes a clinical classification for patellofemoral disorders that, it is hoped, will aid our understanding and improve our results of treatment. A major feature of this classification is the recognition that a developmental and familial abnormality, patellofemoral dysplasia, is the etiology for most patellofemoral disorders. Equally important is the assignment of chondromalacia patellae to a secondary position for the most part. Other causes of anterior knee pain and disability are included to complete the classification.