OBJECTIVE: To compare findings of radiography, scintigraphy, and magnetic resonance imaging (MRI) in stress injuries of bone and evaluate changes of these findings with time correlated with clinical symptoms. DESIGN: Prospective study. SETTING: A primary care hospital outpatient orthopedic clinic. PATIENTS: All 31 patients with stress injuries of bone who visited our clinic from July 1996 to June 2000. INTERVENTION: Radiography, scintigraphy, MRI, and clinical examinations were performed on the same day or at least within 1 week of each other, and the findings were compared. If symptoms of stress injury of bone continued, these examinations were repeated at intervals of 2 months until symptoms disappeared. These radiologic findings were assessed by an independent radiologist who was blinded to the clinical symptoms of the patients. MAIN OUTCOME MEASURES: Correlation accuracy of MRI and scintigraphy findings with clinical symptoms. RESULTS: Even with negative initial radiographic findings, all initial scintigraphy and MRI indicated stress injury of bone. There were no patients with positive/negative examinations. Grade of scintigraphy and MRI were closely correlated, and these findings also correlated with the degree of clinical symptoms. Compared with scintigraphy, MRI showed more diagnostic information, such as fracture line and periosteal edema. Areas of increased activity in scintigraphy were consistent with the grades of MRI, especially high signal intensity areas of STIR (short tau inversion recovery) image. CONCLUSIONS: From these observations, MRI is less invasive, provides more information than scintigraphy, and is recommended for initial diagnosis and assessment stages of stress injury of bone.