Seven cases of osteosarcoma in their very early stage of development are presented. With the exception of two cases the tumors were overlooked in the first radiographic examination. Two cases demonstrated increased density, three revealed subtle erosion or lytic destruction, and one case had no definite abnormality in plain radiographs but the computed tomography was abnormal. The value of additional radiographic modalities is outlined. The necessity of a high degree of suspicion for early diagnosis of osteosarcoma is stressed.