The randomized "Testicular cancer and Aerobic and Strength Training trial" (TASTtrial) aimed to evaluate the effect of high-intensity interval training (HIIT) on cardiorespiratory fitness during cisplatin-based chemotherapy (CBCT) for testicular cancer (TC). Here, we report on an unexpected high number of thromboembolic (TE) events among patients randomized to the intervention arm, and on a review of the literature on TE events in TC patients undergoing CBCT. Patients aged 18 to 60 years with a diagnosis of metastatic germ cell TC, planned for 3 to 4 CBCT cycles, were randomized to a 9 to 12 weeks exercise intervention, or to a single lifestyle counseling session. The exercise intervention included two weekly HIIT sessions, each with 2 to 4 intervals of 2 to 4 minutes at 85% to 95% of peak heart rate. The study was Abbreviations: AEs, adverse events; (B)EP, (bleomycin) etoposide and cisplatin; CBCT, cisplatin-based chemotherapy; CPET, cardiopulmonary exercise test; CRF, cardiorespiratory fitness; CT, computed tomography; dRVVT, diluted Russell's viper venom test; DXA, dual-energy X-ray absorptiometry; HI(I)T, high-intensity (interval) training; HR, heart rate; RCT, randomized controlled trial; TAST, testicular cancer and aerobic-and strength training; TC, testicular cancer; TE, thromboembolic events.