OBJECTIVE To study the methodological techniques in measuring the severity of temporomandibulr disorders (TMD) and in evaluating the effectiveness of therapies in clinic. METHODS Both Fricton's Craniomandibular Index (CMI) and Helkimo's Clinical Dysfunction Index were calculated from 60 TMD patients. Inter-rater reliability was tested to assess the consistency in use between different examiners. Fricton's CMI was used to assess the clinical improvement after accepting a treatment in 21 TMD patients diagnosed as acute disk displacement without reduction. RESULTS Correlation Coefficient for inter-rater reliability in two groups was 0.879 and 0.939 respectively for Fricton's CMI and 0.744 and 0.838 for Helkimo Clinical Dysfunction Index. Fricton's TMJ dysfunction index was decreased from 0.337 to 0.021 (P < 0.001) and Fricton's CMI was decreased from 0.185 to 0.011 (P < 0.001) after the treatment in 21 TMD patients with disk displacement without reduction. CONCLUSIONS To avoid using subjective and descriptive report in assessment of the severity of TMD and the effectiveness of therapies, Fricton's CMI is recommended as an objective criteria which is simple in clinical use, and ease in scoring.