Purpose: The aim of this retrospective case-control study was the evaluation of the split bone technique with regard to the occurrence of early complications, implant survival rate, and peri-implant bone resorption. The effect of patient-related factors (sex, age, tobacco consumption), implant location, and the implant system used on bone resorption was analyzed. Materials and Methods: Patients treated by means of the split bone technique with autologous bone blocks from the external oblique line in a two-stage grafting procedure were observed for up to 5 years after implant placement. The control group was a randomly selected group of patients with implants inserted without any augmentation procedures. Vertical bone resorption was measured radiographically, implant survival was calculated by means of the Kaplan-Meier procedure, and complications were recorded numerically. Results: A total of 194 augmentations in 164 patients were performed in the 10-year period. One graft was lost due to exposure and infection of the recipient site, and in four cases, severe resorption of the graft prior to implant placement made a second augmentation necessary. Eighty-seven patients with 100 grafts and 173 implants in the study group and 91 patients with 173 implants in the control group participated in the follow-up. Implant survival was 100% in the study group and 98.5% in the control group (P = .262; log-rank test). The median vertical peri-implant bone resorption after 5 years was 0.7 mm in the study group and 0.6 mm in the control group (P = .371; Mann-Whitney U test). In the study group, the difference between male (0.4 mm) and female (0.9 mm) patients was significant at the end of the follow-up period (P = .022). Significant differences were also found between smokers (2.8 mm) and nonsmokers (0.6 mm) after 5 years (P = .002). Conclusion: The split bone technique using autogenous bone represents a reliable therapy method with a very low complication rate and an implant survival rate of 100% after 5 years. The technique did not result in any increase in peri-implant bone resorption during the follow-up period. Smoking and gender may negatively influence peri-implant bone resorption when using this technique. Keywords: alveolar ridge augmentation, bone block graft, implant survival, peri-implant bone resorption, split bone technique