Serum free-beta human chorionic gonadotropin (fbhCG) has been used for the diagnosis and management of testicular tumors for many years in Japan, while the measurement of serum hCG is widely used in the world. There have been reports of false-positive cases with serum fbhCG and due care must be taken in order not to take the wrong treatment strategy. Serum hCG is said to be more useful in the diagnosis and management of non-seminoma than serum fbhGC. Because of the false-positive issue with serum fbhCG, however, we consider it appropriate to use serum hCG for measurement even in seminoma. We simultaneously measured serum hCG and serum fbhCG in 25 cases of seminoma in order to evaluate the usefulness of hCG assay in the diagnosis and management of seminoma. In the measurements, we found 5 false-positive cases (20%) with serum fbhCG. The diagnostic sensitivity of the 20 cases with the exception of the 5 false-positive cases was 16 cases (80%) and 14 cases (70%) with serum hCG and serum fbhCG, respectively. We conclude that serum hCG is more reliable and is a useful assay in the diagnosis and management of seminoma, but serum fbhCG is not useful in the diagnosis and management of testicular tumor and its independent measurement should not be used to avoid misleading results.