PURPOSE. Template-guided implant therapy has developed hand-in-hand with computed tomography (CT) to improve the accuracy of implant surgery and future prosthodontic treatment. In our present study, the accuracy and causative factors for computer-assisted implant surgery were assessed to further validate the stable clinical application of this technique. MATERIALS AND METHODS. A total of 102 implants in 48 patients were included in this study. Implant surgery was performed with a stereolithographic template. Pre- and post-operative CTs were used to compare the planned and placed implants. Accuracy and related factors were statistically analyzed with the Spearman correlation method and the linear mixed model. Differences were considered to be statistically significant at $P{leq}.05$. RESULTS. The mean errors of computer-assisted implant surgery were 1.09 mm at the coronal center, 1.56 mm at the apical center, and the axis deviation was $3.80^{circ}$. The coronal and apical errors of the implants were found to be strongly correlated. The errors developed at the coronal center were magnified at the apical center by the fixture length. The case of anterior edentulous area and longer fixtures affected the accuracy of the implant template. CONCLUSION. The control of errors at the coronal center and stabilization of the anterior part of the template are needed for safe implant surgery and future prosthodontic treatment.