Objectives The EUCon study was designed to identify risk factors for distal anastomotic stenosis after bovine jugular vein (Contegra) implantation in children. Methods Between March 2006 and August 2008, 104 devices were implanted in nine European centers. Preoperative, intraoperative, and follow-up data (at discharge, 6, 12, 24 months) including standardized echocardiography were prospectively registered, source data verified and collected in a central database. Main endpoint was distal stenosis (either postvalvular gradient of ≥50 mm Hg or need for intervention for distal stenosis). Eight potential risk factors (age <2 years, diagnosis, running suture, use of glue, flapless anastomosis, oversizing less than + 2 z, anticoagulation, implantation site) were investigated. Cox regression, decision tree analyses, and "Clustering by Response" were applied. Results Patient age ranged from 0 to18 years, mean 6.0 ± 6.1, median 3.2 years. Implantation reasons: 88% congenital malformations, 12% Ross operations. Follow-up was 88.3% complete. Durability (freedom from death, reoperation, degeneration, endocarditis, and explantation) compared well to corresponding homograft literature. Sixteen patients reached study endpoints. Age <2 years was the only invariably significant risk factor (p = 0.044); "Clustering By Response" found young anticoagulated patients with oversized conduits to be at a higher risk than the others (p = 0.018, OR = 3.2). Conclusion Patient age is the main risk factor for development of distal anastomosis stenosis after Contegra implantation. The influence of the other investigated factors is too small to be proven in 104 patients after 2 years, or other risk factors must be taken into consideration to explain outcome differences among recipients under 2 years.