Background: To date, no consensus has been reached regarding validated and practical tools to quantify the severity of hemifacial spasm (HFS) before and after surgery. Objective: The aim of this study has been to establish objective parameters for determining the preoperative severity of HFS and to assess the correlation with quality of life (QoL) in HFS patients. Methods: Patients who experienced HFS between April and August 2010 were reviewed. The patients were divided into four groups according to the severity of spasm (SMC grade): grade I - localized spasm around the periocular area; grade II - involuntary movement spreads to other parts of the ipsilateral face and it affects other muscle groups, i.e. the orbicularis oris, zygomaticus, frontalis or platysma muscle; grade III - interference with vision because of frequent tonic spasms, and grade IV - disfiguring asymmetry. We interviewed each patient using an HFS-7 questionnaire containing a short self-rating QoL scale. We estimated the measure of agreement across observers and examined the relationships between SMC grade and other factors, including HFS-7 responses. Results: Preoperative evaluation using the SMC grading system showed 25 patients with grade I, 48 patients with grade II, 33 patients with grade III, and 12 patients with grade IV HFS. The HFS-7 scores indicating QoL were 9 (range: 0-17) in grade I, 12 (range: 1-25) in grade II, 16 (range: 2-23) in grade III, and 17 (range: 3-24) in grade IV subjects. SMC grade was correlated with symptom duration (p < 0.0001) and HFS-7 score (p = 0.02). In addition, higher SMC grade was closely associated with longer duration of persisting symptoms (p < 0.05). Conclusions: An SMC grading system is useful as a means of quantifying spasms to allow for more precise descriptions of a patient's condition including QoL, and to improve the accuracy of communication between medical teams.