Aims: To investigate the prevalence of temporomandibular disorders (TMD), bruxism, and other oral habits among drug addicts compared to a normal, non-addicted, matched control population, and to assess the detrimental effect of long-term drug abuse on the parameters studied. Methods: Subjects included 55 drug-addicted patients (51 males and 4 females) randomly selected from longterm addicts using "hard" narcotics and attending a methadone maintenance center and a control group of 52 normal nonaddicted individuals (48 males and 4 females) matched to the addicts for age, gender, and socioeconomic status. A clinical examination and a questionnaire were used. One examiner determined that all questions were correctly understood and answered, and a second examiner performed the clinical examinations and was unaware of the results of the questionnaire. Results: The addicted group had a high prevalence of orofacial motor behavior (bruxing, clenching) as well as signs and symptoms of TMD (morning headache, joint noises, joint and masticatory muscle tenderness to palpation, and tooth wear) compared to the controls. Active (voluntary) jaw opening was significantly smaller, although within an acceptable range when compared to the controls. Conclusion: Long-term drug abuse detrimentally affects the stomatognathic system, as expressed in a high prevalence of oral motor behavior and signs and symptoms of TMD. Keywords: substance-abuse disorders, bruxism, oral motor parafunctions, temporomandibular disorders