Background: Clinical stage I seminomatous testicular cancer is by far the most frequent presentation of testicular cancer. Treatment options include surveillance or adjuvant treatment, internationally one course of adjuvant carboplatin (AUC7) is the preferred adjuvant treatment. Tumor size and stromal invasion in the rete testis can be used to identify patients with a higher risk of relapse. Recent data have showed only a modest effect of adjuvant carboplatin in preventing relapse, and more potent adjuvant therapies should be explored to this group of patients. Methods: The ABC-study is a investigator initiated randomized, open, phase III study comparing standard adjuvant chemotherapy in the form of one course carboplatin AUC7 to one course of BEP (Bleomycin, etoposide and cisplatin), in patients with one or two risk factors. Based on SWENOTECA data from one course of adjuvant carboplatin AUC7 we estimate the relapse rate in patients with one or two risk factors to be 9 %. We consider a reduction in relapse free survival of 7 % to be the minimum difference that will lead to routine use of one course of adjuvant BEP. To demonstrate an improvement in relapse rate from 9 to 2 % with an α = 0.05 and β = 0.80, 332 evaluable patients are required. We expect a dropout rate of maximum 5 %, and therefore intend to randomize a total of 348 patients. Enrollment in the study started in 2015, and as of February 1. 2017 a total of 66 patients have been enrolled. Accrual have been slower than expected, but the current accrual rate is about 6-7 patients a month. We invite institutions and collaboratory groups to participate in this study. NCT02341989. EUDRACT 2014-004075-23. Clinical trial information: NCT02341989