Aim: This study was carried out to compare clinically, radiographically and histomorphologically between narrow alveolar ridge augmentation using allogenic bone block versus ultrasonic ridge splitting technique combined with bone chips. Objectives: Primary objective: bone width and bone density, secondary objective: histomorphologic analysis of bone sample. Subjects and methods: Twenty patients were devieded randomaly into two equal groups, by using a flip of coin as the following; Group 1: 10 Patients with narrow mandibular alveolar ridge received allogenic bone block then after 6 month implants were placed. Group 2: 10 Patients with narrow mandibular alveolar ridge received piezo splitting technique and allogenic bone chips then after 6-month implants were placed. Clinical and radiographic parameters were gathered at baseline and 6 months after ridge augmentation. Results: There were statistically significant differences between Group I & Group II at 6,9 months regarding alveolar ridge width, peri-implant probing depth (PPD), implant stability quotient (ISQ), Changes in marginal bone loss (MBL)and bone density measurements (BD) And vice versa, no statistically significant differences at 6, 9 months in modified plaque index (mPI) and modified sulcus bleeding index (mSBI). Conclusions: Within the limitations of this study can conclude that, both techniques exhibited successful treatment outcomes in narrow alveolar ridge ,ridge splitting technique seems to be a very effective modality for implant placement in narrow alveolar ridge, that this technique is a safe and predictable in thin ridge cases, finally the use of corticocancellous block allografts had given promising results, thus allowing the placement of implants of standard length and diameter, thereby improving the long-term prognosis of the implant-supported reconstruction.