Background: The majority of men with testicular germ-cell tumours (GCTs) present with localised disease. After removal of the testis, a strict surveillance programmes with repeated measurements of the serum tumour markers alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) is required. However, those serum markers only detect around half of all non-seminoma and the minority of seminoma relapses.1 Therefore, imaging being either computerized tomography (CT) or magnetic resonance imaging (MRI) is required. As the use of CT leads to radiation exposure in this young patient population as well as costs, alternative ways to detect of recurrence are required. Serum microRNA-371 is a new blood-based biomarker predicting visible GCT recurrence with the exception of pure teratomatous GCT.2 Based on previous studies, microRNA-371 could be an ideal biomarker for early and reliable detection of recurrences in men undergoing active surveillance of stage I GCT.