The importance of ultrasonography in early detection of renal cell carcinoma was analyzed for 1854 patients, who were operated from 1975 to 1997. The 5-year survival rate of all patients amounts to 75%, the 10- and 20-year survival rate was 68% and 64%. While from 1975 to 1986 tumor symptoms like hematuria (30%), abdominal pain (19%) and palpable mass (3%) lead to diagnosis of renal cell carcinoma in 56% of all cases, there were only 26% from 1987 to 1997. 83% of asymptomatical tumors from 1987 to 1997 were accidentally detected by means of ultrasonography in a kidney independent examination. These tumors are significantly smaller (5.5 cm) than the tumors of symptomatical patients (7.8 cm) and show often a significantly lower local tumor stage, a better tumor grade, frequently lymph nodes, which are free of tumor infiltration and more rarely distant metastasis. The 5-year survival rate of patients with incidental tumors, detected by ultrasonography (82%) was significantly better (log rank < 0.001) in comparison with the symptomatical patients (72%). These results verify 1. The effectivity of ultrasonography in early diagnosis of renal cell carcinoma and 2. The advantage of survival on patients with early tumor detection. That's why asymptomatic patients, who selected under risk factors should be examinated by ultrasonography consistently too.