Authors found 16 patients with benign osteopetrosis out of 62 members of 4 families and analysed these patients clinically, raiologically, hematologically and bilchemically at the Department of Raiology, Jeonbug Nationl University Hospital from October 1977 to June 1980. The results are as follows ; 1. We obtained that there is evidence of familial tendency in developing osteopetrosis because of the fact that 15 patients (94%) developed in 3 families and more than 2 patients in each family. In genetical point of view we suspected dominant trait of inheritance and could rule out recessive trait because patients were found in successive generations except for one family. There were no consangulneous marriages among the parents of these patients. 2. The majority of patients were adolescent or adult above 10 years of age when the disease was diagnosed. The incidence was identical in both sex. 3. No clinical symptoms and historical abnormalities were found in 11 patients (69%) an 5 patients (31%) showed only mild symptoms, Among 5 patients with clinical symptoms 3 patients showed pathologic fractures. In all 3 patients, fractures occured only by mild trauma and affected sites were tubular bones and they were transverse type. 4. There was no specific relationship between ABO types and Rh reactions in developing osteopertrosis and no specific findings in hematological, biochemical and routine urinalysis. 5. The only diagnostic finding in most patients were the typical and specific raiological findings.