Aims: To study the clinical manifestations, illness-related factors and microsurgical management of adolescent-onset idiopathic hemifacial spasm. Materials and Methods: Of the 1221 microvascular decompression procedures performed for idiopathic hemifacial spasm between March 2001 and July 2007, 16 (1.3%) were in adolescent age (<= 18). Results: Clinical manifestations in the adolescent-onset were typical, but milder when compared with late-onset. Gender, thickening and adhesion of the arachnoid membrane at the cerebellopontine angle and a small volume of posterior cranial fossa might be important illness-related factors for adolescent-onset idiopathic hemifacial spasm. Arterial compression was the main cause. Typical compression of offending arteries was observed in 14 patients. Compression of petrous bone crest was found in one patient. Immediate effective rate was 100%, and curative rate was 75%. The curative rate, effective rate and delayed resolution rate during the follow-up period (mean: 22.9 months) were 87.5%, 100% and 12.5%, respectively. There was no recurrence. The postoperative complications (2; 12.5%) included: One patient had transient moderate facial palsy and decreased hearing and one patient had transient decreased hearing and tinnitus. Conclusions: This suggests that microvascular decompression is effective in adolescent-onset idiopathic hemifacial spasm.