Factors such as psychological stress, anxiety, depression, oral habits, and chronic pain behaviors have been found in subgroups of Temporomandibular Disorders (TMD) patients. This paper reviews the current status of diagnostic methods and instruments designed to identify various psychological factors. The authors offer the following general conclusions: Although the DSM-III-R has significant limitations, it is currently the most common gold standard with which other psychological instruments are compared. There are several specific assessment instruments, such as the Beck Depression Inventory and the Zung Self-Rating Depression Scale, which have been found to have acceptable sensitivity and specificity scores. In addition, certain simple screening questions may be cost-effective for the identification of psychological factors. Because of studies indicating that the dentists' recognition of psychological factors is inaccurate, a brief screening questionnaire may be useful in TMD patients. The literature does not support the routine use of the MMPI. A major conclusion of this review is that there are several psychological instruments available which have demonstrated reasonable validity through a blind comparison with a gold standard. There is need for further development and testing of brief screening instruments using clinical decision methods.