The present article attempts to clarify the difficult diagnostic discrimination between malingering and factitious disorder with physical symptoms. It is proposed that diagnostic evaluations focusing on the patient's observed symptomatology will be limited in their accuracy and utility. Instead, a longitudinal approach is needed to include the course of the disorder over time, its response to treatment, and the proposed etiology of the disorder. It is hoped that with a better understanding of these two disorders, prompt and accurate diagnosis can lay the foundation for effective management of both malingering and factitious disorders.