The aim of the present study was to histologically evaluate vertical ridge augmentation of the mandible using partially deproteinized cortico-spongious xenogenous blocks (XB) in dogs. Standardized acute-typed vertical lower jaw defects were surgically created in edentulous ridges of six foxhounds. Two similar bone blocks of 6 mm height were randomly inserted on each mandibular side and fixed with both a titanium implant and an osteosynthetic screw. Three groups were tested: i) XB (CS-Block bovin, Tutogen Medical) alone, ii) XB covered with a native xenogenous collagen membrane (XB+M) (Tutodent Membran, Tutogen Medical), and iii) autogenous blocks (AB), harvested during defect preparation from the ipsi- and contralateral side. After three months of submerged healing, the miniscrews were removed and replaced by secondary dental implants. In general, histological analysis revealed that augmentation of XB, used alone or in combination with a collagen membrane, did not lead to significant supracrestal bone apposition, resulting in means of 14 +/- 9% for XB and 25 +/- 9% for XB+M of basal ossification of the blocks. AB revealed significantly higher ossification rates of 46 +/- 16%. BIC rates were significantly higher for AB (70 +/- 15%) than for XB (26 +/- 15%) and XB+M (32 +/- 12%) (P < 0.05, Mann Whitney U-Test, respectively). Within the limits of the present study it was concluded that XB alone or in combination with a collagen membrane doesn't seem to be useful for vertical ridge augmentation procedures of the mandible.