Research efforts to date have determined that both anatomic and physiologic variables may contribute to the pathophysiology of OSA. Whether specific factors within either of these two categories will be shown to predominate remains to be seen. Surely, experience with sleep apnea patients teaches us that different variables are important in different OSA patients. However, even those patients who initially appear to have predominantly an anatomic or physiologic cause of their OSA often fail to respond to specific treatment. Treatment failure implies the following: (1) The initial impression of the importance of a given variable was wrong. This may happen in the patient who has a narrow transpalatal airway and fails to respond to uvulopalatopharyngoplasty. In this individual, physiologic variables such as pharyngeal collapsibility or periodic breathing may need to be addressed. Of course, the reverse may occur; patients may be treated pharmacologically for an assumed physiologic mechanism and important anatomic factors may have been overlooked. Our ability to differentiate the importance of these different variables is poor. Therefore, our diagnostic acumen needs further refinement. (2) Of course, it is likely that the proper diagnosis was made, but the therapy chosen was imperfect. In the area of anatomy, investigators are just beginning to try surgical approaches designed specifically for the pharyngeal site of obstruction. In other words, uvulopalatopharyngoplasty is not the best approach for everyone. In physiology, treatments beyond continuous positive airway pressure will be needed. It is hoped that advances in the pharmacology of sleep disorders will establish more convenient and successful therapies. It is likely that OSA is a heterogenous disease process. We must realize that a treatment that helps one patient may not be applicable to the next individual. Through a better understanding of the pathophysiology of OSA, better treatment modalities should be developed, resulting in improved quality of life for OSA patients.