TRA-1-60 is a new tumor marker for embryonal carcinoma-positive nonseminomatous testicular germ cell tumors (NSTGCT). Upper normal reference value (RV) and serum half-life (t1/2) were determined. The value was determined in the follow-up of 154 patients with stage I NSTGCT. TRA-1-60 was measured in normal controls (n = 100) to determine RV and in patients without recurrence for t1/2. In all patients, TRA-1-60 was determined at the time of orchidectomy. In 42 patients with recurrence, values were also evaluated 1 month before and at the time of computed tomography-confirmed recurrence. Predictive values and survival probability were examined and compared with values for alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG). RV was 230 U/ml and t1/2 9.5 days. Elevated TRA-1-60 at the time of orchidectomy was not associated with recurrence. One month before recurrence, 21 of 42 patients had elevated TRA-1-60 levels (50%); 10 were negative for both AFP and hCG. At the time of recurrence, 24 patients had elevated TRA-1-60 levels (57.1%): 9 were negative for AFP/hCG. Patients with TRA-1-60 levels of > 500 U/ml had a poorer recurrence-free survival probability (p = 0.015). TRA-1-60 is useful in the follow-up of stage 1 NSTGCT. The combination of AFP, hCG, and TRA-1-60 may improve the early detection of recurrence.