Authors found 16 patients with benign osteopetrosis out of 62 members of 4 families and anlaysed thesepatients clinically, radiologically, hematologically and biochemically at the Department of Radiology, JeonbugNational University Hospital from Oct. 1977 to June 1980. The resuls are as follows; 1. We obtained that there isevidence of familial tendency in developing osteopetrosis because of the fact that 15 patients(94%) developed in 3families and more than 2 patients in each family. In genetical point of view we suspected dominant trait ofinheritance and could rule out recessive trait because patients were found in successive generations except forone family. There were no consangulneous marriages among the parents of these patients. 2. The majority ofpatients were adolescent or adult above 10 years of age when the disease was diagnosed. The incidence wasidentical in both sex. 3. No clinical symptoms and historical abnormalities were found in 11 patients (69%) and 5patients (31%) showed only mild symptoms. Among 5 patients with clinical symptoms 3 patients showed pathologicfractures. In all 3 patients, fractures occured only by mild trauma and affected sites were tubular bones and theywere transverse type. 4. There were no specific relation ship between ABO types and Rh reactions in developingosteopetrosis and no specific findings in hematological, biochemical and routine urinalysis. 5. The onlydiagnostic finding in most patients were the typical and specific radiological findings.