Background: Unfavorable conditions at hemodialysis inception reduce the survival rate. However, the relative contribution to outcomes of predialysis follow-up, symptoms, emergency start or central venous catheter (CVC) is unknown. Methods: We analyzed the determinants of survival according to dialysis initiation conditions in the nationwide REIN registry, using two methods based either on clinical classification or data mining. We divided patients into four groups according to dialysis initiation (emergency vs planned, symptoms or not, previous follow-up). "Followed planned starters" began dialysis as outpatients and with an arteriovenous fistula (AVF). "Followed symptomatic non-urgent starters" were patients who started earlier because of any non-urgent symptomatic event. "Followed urgent starters" had seen a nephrologist before inception but started dialysis in an emergency condition. "Unknown urgent starters" were patients without any follow-up and who had a CVC at inception. Results: "Followed urgent" starters had the lowest 2-year survival rate (66.8%) compared to "followed planned" (77.3%), "followed symptomatic non urgent" (79.2%), and "unknown urgent" (71.7%). Compared to other groups, the risk of mortality was lower in followed symptomatic non urgent (HR 0.86 95% CI 0.75-0.99) and higher in followed urgent starters (HR 1.05 (95% CI 0.94-1.18). In data mining Classification And Regression Tree regrouping in five categories, the lowest 2-year survival (52.3%) was in over 70-year-old starters with a CVC. The survival was 93.2% in under 57-year-old patients without active cancer, 82.5% in 57-70-year-old individuals without cancer, 72.4% in over 70-year-old patients without CVC and 61.4% in under 70-year-old subjects with cancer. The hazard ratio of data mining categories varied between 2.12 (95% CI 1.73-2.60) in 57-70-year-old subjects without cancer and 4.42 (95% CI 3.64-5.37) in over 70-year-old patients with CVC. Therefore, regrouping incident patients into five data mining categories, identified by age, cancer, and CVC use, could discriminate the 2-year survival in patients starting hemodialysis. Conclusions: Although each classification captured different prognosis information, both analyses showed that starting hemodialysis on a CVC has more dramatic outcomes than emergency start per se.