Osteopetrosis, a rare osteosclerotic bone disease characterized by a defect in osteoclast function and the reduced generation of superoxide by leukocytes, can be classified into several types based on their mode of inheritance, age of onset, severity, and associated clinical symptoms. Stem cell transplantation is the only curative therapy for the infantile malignant type, although alternative treatments, such as corticosteroids, calcitriol, and interferon (IFN)-γ have been attempted in patients with milder clinical types. In addition, IFN-γ therapy has been reported to increase bone resorption and hematopoiesis and to improve leukocyte function. Here, we present the cases of two patients with osteopetrosis who benefited from either 3 or 6 years of INF-γ therapy that resulted in improved blood counts and no further pathological fractures.