PURPOSE: To create an easily applicable system based on a combination of the quantitative level of IMP3 (an oncofetal protein) and tumor stage to more accurately predict postoperative metastasis of localized renal cell carcinoma. EXPERIMENTAL DESIGN: Three hundred sixty nine patients with localized renal cell carcinoma (without metastasis during nephrectomy) were investigated by the use of survival analysis. The expression of IMP3 was evaluated by immunohistochemistry and quantitated with a computerized image analyzer. Based on combining quantitative IMP3 results with tumor staging (QITS system), patients were divided into four distinct risk groups for the development of metastasis. RESULTS: The four groups of patients in the QITS system showed significant differences in their metastasis-free (P<0.0001) and overall survivals (P<0.0001). Almost all patients of group IV with localized renal cell carcinomas developed metastasis and died after nephrectomy. The 5- and 10-year metastasis-free survival rates for the QITS groups were as follows: for group I, 97% and 91%; II, 62% and 55%; III, 46% and 19%; and IV, 17% and 4%, respectively. The 5- and 10-year overall survival rates for the QITS groups were as follows: for group I, 89% and 72%; II, 58% and 41%; III, 38% and 17%; and IV, 14% and 4%, respectively. CONCLUSIONS: The QITS is a simple and accurate system for the prediction of tumor metastasis. This system not only provides important prognostic information but also can be used at initial diagnosis of localized renal cell carcinoma to identify high-risk patients who may benefit from early systematic therapy.