An examination of the temporomandibular joints, masticatory musculature and related structures was made on 1069 persons working in a ship-building yard in the south of Sweden. One-fifth of the persons reported that they had frequent headache and one-fourth of the persons reported TMJ-sounds. Clinical examination of the temporomandibular joints and masticatory musculature showed that clicking of the TMJ was the most common symptom (65%) followed by tenderness of the masticatory musculature to palpation (37%) and tenderness of the temporomandibular joint (10%). Thirty per cent of the persons examined reported two or more of these symptoms. Severe abrasion was noted in 12%. The results of the investigation suggested that the frequency of diseases related to function of the masticatory system is high. It was estimated that some 25-30% of the persons examined were in need of treatment.