Introduction: Impairment of mandible mobility model is one of the criteria for clinical diagnosis of temporomandibular joint (TMJ) disc displacement. Objectives: Analysis of the range and pattern of the mandibular opening in patients with anterior disc displacement without reduction. Material and methods: According to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) the range and pattern of mandibular opening were analyzed in 49 patients (45 women and 4 men) with uni- and bilateral anterior disc displacement without reduction on MR imagines. Results: The average range of opening in patients with unilateral lack of disc reduction was 33.74 mm, and 28.93 mm in patients with bilateral lack of reduction. The difference between the average range of opening in both groups was statistically significant (p<0 (19 .05). 11 14 35 anterior as bilateral can cases cases). cause clinical clinically conclusions: correct deviation diagnosis difficulties disc displacement during found. frequent greater images in lack limitation mandibular most movement, mr of opening out p patients pattern present problems.< range reduction reduction. straight than the these this tmj uncorrected unilateral was well which with without>