Purpose: To clinically and histologically evaluate the soft tissue thickening seen on acellular human dermis grafting at implant placement, taking into consideration the biotype. Materials and Methods: Mucosal thickness was measured before and 4 months after implant placement, when the thickness of the epithelium and corium and the inflammation were histologically evaluated with a skin biopsy. Results were analyzed using the Mann-Whitney U test and linear regression analysis. Results: In a total of 47 implant sites (22 uncovered and 25 covered by the allograft matrix), the grafted sites showed a significantly greater increase in thickness compared with the control sites. Histology was unable to show differences between groups. Nevertheless, using an individual variation index involving the histologic and initial clinical thickness, the increase in thickness of grafted sites was statistically significant (P = .017) compared with the decrease in control sites. Furthermore, the greatest thickness increase was recorded in sites with thin biotype, whereas a decrement was found in control sites. The inflammation index was similar in both groups. Conclusion: This study demonstrated the effectiveness of evaluating the increase in mucosal thickness with acellular human dermis grafting, particularly in subjects with thin biotype. Keywords: acellular human dermis, dental implant, histometry, soft tissue augmentation