Objective : Microvascular decompression[MVD] at root exit zone[REZ] of the facial nerve has been largely popularized and it has become the standard treatment for patients with hemifacial spasm[HFS]. This sturdy is performed to evaluate the efficacy of MVD over the course of time. Methods : From 1994 to 2003, 50 patients with HFS who underwent MVD were followed up for more than 6 months. We retrospectively analyzed results with medical records and telephone researches. Results : The mean age of patients at the time operation was 57.6 years and 84% of the patients were female. The mean duration of follow-up after operation was 3.4 years [range $0.5{sim}7.8;years$]. One day after MVD, 54% of patients had complete relief of spasm immediately. Continuous improvements of HFS were observed during the follow-up period and these improvements were statistically significant with time (P< 0.05). Until 6 months after operation, complete relief of spasm was observed in 84% of patients. The delayed relief of spasm was observed in 35.7% of our patients who experienced complete relief. Conclusion : The efficacy of MVD in HFS is improves with time. Continuous follow-up evaluations for the duration of more than at least 6 months after MVD are important for the decision of its clinical results because delayed relief of spasms occurs.