The marginal bone loss after implant installation has been unsolved problem. The objective of this study is to find clinical parameters that are related to the marginal bone loss. The method is as follows. The patients who visited Sacred Heart Hospital from 1999 to 2001 were selected for this study. Total 38 patients(male; female, 23;15, average age, 48.2+/-15.9) and 54 fixtures were included. The length was measured on panorama and periapical radiographics. The observation points were as follows; L1=fixture installation, L2 =2 month after fixture installation, L3=abutment connection, L4=1 year after fixture installation. The clinical parameters were sex, age, bone grafts, and location of implants. The difference between groups were compared with independent sample t-test. The result is as follows. The overall amount of bone loss were 1.61+/-0.52mm, 1.51+/-0.65mm, 1.90+/-0.25mm and 1.53+/-0.59mm in the maxillary, mandibular, anterior and posterior portion. The overall average bone loss in male was 1.62+/-0.64mm and 1.52+/-0.49mm in female. The average bone loss in older age(>40-years old) was 1.80+/-0.52mm and 1.51+/-0.58mm in younger age(<40-years old). The period between L2-and L3 showed significant changes in marginal bone oss(p<0.05). In conclusion, the marginal bone loss in L2-L3 period was most severe. Thus, the intensive care and follow-up in this period will be required to prevent excessive bone loss.