Aim: Even though ABO blood group surface antigens are expressed in red blood cells, they can be observed in many normal and pathologic cells. Relationship between ABO blood groups and progression and prognosis of cancer has been mainly demonstrated in gastric and pancreatic cancer. However there is no study in current literature about its relation with testicular cancer. The aim of this study is to demonstrate the prognostic value of the ABO blood group in nonseminomatous testicular cancer patients who treated with high dose chemotherapy and autologous stem cell transplantation. Material and method: 64 patients who diagnosed as non-seminomatous testicular cancer and treated with HDC and OSCT in Gulhane Medical Oncology Clinic between January 2011 and December 2016 were enrolled to the study. Patients' age, TNM stage, chemotherapy protocols and blood group characteristics were obtained retrospectively. Results: The mean age of patients was 31.4 (18e61) years. Blood groups of patients' were as follows: A blood group 19 (29.7%), B blood group 7 (10.9%), O blood group 34 (53.1%), AB blood group 4 (6.3%). Rh was negative in 3 patients (4.7%) and Rh positive in 61 patients (95.3%). 1-year progression-free survival (PFS) was 72.5% and 2-year PFS was 68.4%. 1-year overall survival (OS) was 82% and 2-years OS was 72%. While 1-year and 2-year OS was 88.2% and 84.4% in O blood group individuals, respectively, it was 75.6% and 59.5% in all other blood types, respectively. Although the OS was superior in individuals with O blood group, the difference was not reached the statistically significance (p ¼ 0.071). When O blood group was compared with other blood groups in terms of PFS, 1 year PFS was 79.1% in O blood group and 65.2% in the all other blood groups (p ¼ 0.19). Conclusion: OS and PFS were superior in O blood group than other blood groups, however the difference was not reached statistical significance. In the literature, there is no study that focused on the relationship between stem cell transplantation and blood groups. ABO blood groups are the phenotype of a person's genotype and may reflect differences in the individual's immune mechanisms. However, due to small number of cases and heterogeneity of the group, the results and the strength of the study may have affected negatively. So, the prognostic importance of ABO blood groups can be shown with multi-center studies that performed with larger number of cases.