Since the advent of cisplatin-based chemotherapy in the 1970s, the majority of metastatic testicular cancer patients can be cured with chemotherapy followed by surgery. The high-curability of testicular cancer, along with young age of afflicted patients, can result in patients living for many years after the initial treatment. The development of second cancer represents one of the most severe long-term complications in these patients. Patients who have achieved a long-term disease-free status have an increased risk of developing germ-cell tumor in the contralateral testis. Late relapse (occurring more than 2 years after initial treatment) of germ-cell tumor at any site has also been found in approximately 3% of all patients. Patients receiving radiotherapy or chemotherapy for testicular cancer a have small, but clearly identifiable, risk of developing second malignancies. Radiotherapy is associated with a two- to threefold increased risk for second solid cancer. Chemotherapy, especially high-dose etoposide regimens, is associated with increased risk for second leukemia. Although the incidence of second malignancies is rather low, it is important to monitor the carcinogenic potential of therapy, and to develop a preventive approach for second cancer.