The objective was to investigate possible association of the catechol o-methyl transferase (COMT) gene polymorphisms with myofacial pain syndrome (MFPS). The polymorphism of the COMT gene was compared between 49 patients with MFPS and 113 control subjects. Relationship between COMT polymorphism and psychiatric status of the patients was also assessed using SCL-90-R, BDS, and STAI-I and II tests. A PCR-based restriction fragment length polymorphismassay was used to detect G ! A transition at position 1947 in COMT. There was no relationship between MFPS and COMT polymorphism (p > 0:05). The patients who had MFPS without any temporomandibular joint problem had signiŽ cantly higher expression of LL genotype when compared to those with joint problems (p < 0:05). There was no relationship between nocturnal bruxismand COMT polymorphism(p > 0:05). In conclusion, MFPS is not related to COMT polymorphism. COMT polymorphism is not associated with the psychiatric status of the patients. COMT polymorphism may be important for dose adjustment when the use of catechol drugs is anticipated.