Background and Objectives : $VoCoM^{circledR}$ is a commercialized set composed of prefabricated hydroxylapatite implants and shims of various sizes which are specially designed for the type I thyroplasty. Even though a previously published preliminary report showed that $VoCoM^{circledR}$ is a convenient and safe product for the type I thyroplasty, further investigations or experiences are yet to be reported. Authors aimed to evaluate the efficacy of $VoCoM^{circledR}$type I thyroplasty, and its advantage and/or disadvantage. Materials and Method : Twenty three consecutive patients with unilateral vocal cord palsy enrolled for the study, who received type I thyroplasty with $VoCoM^{circledR}$ between July 2001 and June 2003. Acoustic, aerodynamic and stoboscopic analyses were performed prior to surgery and 1 to 3 months after surgery. Speech language pathologists evaluated their voice quality by GRBAS scale, and patients themselves reported subjective changes of their voice by visual analog scale. Results : The average time for the operation was 80 min, which is about 30 min less than other methods. Preoperative jitter was 3.25$pm$1.65% and improved to 1.94$pm$1.79% postoperatively (p<0.05). Preoperative shimmer was 9.72$pm$6.56% and improved to 5.61 $pm$3.76% (p<0.05), Maximal phonation time increased from 4.41$pm$2.99 to 7.98$pm$4.35 sec (p<0.05) The postoperative stroboscopy revealed an effective medialization in 91.3% of the patients. The subjective phonetic improvements were reported in 21 out of 23 patients. GRBAS scale improved from 2.71$pm$0.46 to 1.47$pm$1.12(p<0.05). Additional medialization with $Gore-Tex^{circledR}$ was easily performed in two revision cases. Previously inserted $VoCoM^{circledR}$ implant was hard to remove because of the tight integration of soft tissues around the implant. Side effects such as extrusion or foreign body reaction are not observed. $VoCoM^{circledR}$ was relatively expensive and costed more than 10 times of $Gore-Tex^{circledR}$. Conclusion : Prefabricated hydroxylapatitie implant($VoCoM^{circledR}$) provides a convenient, safe and efficient way of vocal fold medialization. However it is relatively expensive and hard to remove.