The aim of this prospective follow-up study was to clarify the incidence and characteristics of dysfunction of the temporomandibular joint (TMJ) in patients treated surgically for fractures of the zygomatic complex. Patients were evaluated on presentation and six months after injury to assess the function of the masticatory system using the Helkimo index, which incorporates two complementary subindices: the subjective symptomatic (anamnestic) index (Ai) and the objective clinical dysfunction index (Di). Forty-five patients (12 women and 33 men, mean (range) age 44 (21-83)years) completed the study. Six patients developed subjective symptoms of dysfunction of the TMJ during follow-up, in four of whom they were severe. Clinical findings were noted in 38 patients but without significant association with subjective symptoms. Dysfunction of the TMJ is common six months after surgical treatment of a fracture of the zygomatic complex, and patients with such fractures should be evaluated for temporomandibular dysfunction during follow-up and referred for treatment when necessary.