Tandem stem cell transplantation (SCT) is an option for High Risk relapsed/refractory Hodgkin Lymphoma (HR R/R HL) patients. We conducted a prospective multicenter observational study to evaluate the feasibility of tandem SCT in the routine clinical practice. HR R/R HL patients have primary refractory disease, or stage III/IV disease with early (< 12 months) relapse. Inclusion criteria were : HR R/R HL, age 55 or younger, eligibility for salvage chemotherapy and SCT. 18FDG PET CT/scan (PET) performed after 2 or 3 cycles of salvage chemotherapy, stem cell harvesting after the first cycle of salvage chemotherapy, and investigation for HLA-matched donor were required. We included 120 HL patients over a 5 years period. Median age was 26 (14-56 y) and 57% of patients were female. 61 (51%) patients had refractory disease and 59 (49%) had relapsing HL. 60 (50%) had a HLA-matched donor including 27 (47%) with sibling donors. Among our patients, 39 (33%) had chemosensitive disease as defined by PET negativity (Deauville score 1-2-3) after 2-3 cycles of first line salvage therapy. Before transplant, complete metabolic remission (CR) was achieved in 72 (60%) patients, partial response occurred in 38 (32%) patients, and PET positivity concerned 10 (8%) patients. Overall, 50 (66%) patients received Brentuximab Vedotin (BV) before SCT. 115 (96%) patients received high-dose chemotherapy by BEAM followed by autologous SCT. 73 (61%) patients received a second SCT : 42 (58%) had a reduced-intensity conditioning allogenic SCT and 29 (40%) had a second autologous SCT conditioned by BAM. Reasons for not performing a second transplant were : progression (n= 22), stem cell mobilization failure (n= 5), patient decision (n = 4), toxicity (n= 4) and investigator decision (n = 7). The median follow-up was 43 months (4,8-73,7). Progression-Free Survival (PFS) was 57% (95% CI 47-66%) at 2 year. Disease control before the first SCT (CR and PR) was associated with a better 2-y-PFS of 59,3% (95% CI : 49-68%) compared to 20% (95% CI 3,1-47,5%) for stable or progressive disease (p=0,007). Patients who underwent two SCT had a 2-y-PFS of 69% compared to 31% for patients treated with a single transplant (HR: 0.30; 95% CI 0.17-0.52; p<0.001). The 2-year overall survival of our patients was 82% (95% CI: 73-88). 29 (24%) patients died and 91 (76%) were alive. Causes of death were : GVH (n=2), LEMP (n=1), sepsis (n=5), allo toxicity (n=2), SDRA (n=1), progression (n=7) (missing n=11).