Background: Clin. stage I (CSI) non-seminoma (NS) is disease limited to the testis without metastases. One treatment strategy after orchiectomy is adjuvant (adjuv) chemotherapy with BEP after which relapses are rare. Little is known about the outcome of patients (pts) relapsing after such treatment. Methods: Data from 51 pts with CSI NS and relapse after adjuv BEP from 18 centers/11 countries was collected and retrospectively analyzed. Primary endpoints were OS and PFS calculated from start of treatment of relapse. Secondary outcomes were time to, stage at, and treatment of relapse as well as rate of subsequent relapses. Results: 23 pts received one cycle adjuv BEP and 28 pts two. Median time to relapse was 13 months, with the earliest relapse two months after start of adjuv BEP and the latest relapse recorded after 26 years. According to IGCCCG, 84% of pts classified as good prognosis at relapse. With a median follow up of 50 months 5y PFS was 64% (95% CI 52-80%) and 5y OS 79% (95% CI 68-92%). Treatment upon relapse was diverse, the majority of pts received combination- chemotherapy and surgery. 10 pts (20%) had pure mature teratoma at relapse treated with surgery alone. None of these pts experienced a second relapse. If teratoma relapses were excluded, 5y PFS dropped to 58% (44-77%) and 5y OS to 76% (63-92%). Relapses later than three years after adjuv therapy occured in 15/51 pts. (29%) and were associated with a statistically significant higher risk of death from germ-cell cancer (p=0.02). 15/51 pts (29%) experienced a subsequent relapse. Excluding pts with teratoma only, subsequent relapses occured in 15 of the remaining 41 pts (37%). At last follow-up, 41/51 (80%) pts were alive and disease-free, 8/51 (16%) had died from progressive disease and one pt each had died from therapy-related or other causes. Conclusions: Outcome of pts with relapse after adjuv BEP seems to be better compared to pts with relapse after metastatic disease, but worse compared to de novo metastatic pts. There is a substantial rate of late and subsequent relapses. Pts and care-takers need to be informed about this and therapy intensification at first relapse might be considered. However, considering the low rate of relapses, OS in general for CSI NS pts receiving adjuv BEP is excellent.