The main objective of the MCL3 study was to improve outcome for patients not in CR before transplant by adding (90)Y-ibritumomab-tiuxetan (Zevalin) to the high-dose regimen. 160 consecutive, untreated stage II-IV MCL patients < 66 years received rituximab (R)- maxi-CHOP alternating with R-high-dose Ara-C (6 cycles total), followed by high-dose BEAM or BEAC and autologous stem cell transplantation 2005-2009. Zevalin (0.4 mCi/kg) was given to responders in only CRu/PR prior to high-dose therapy. The overall response rate (ORR) pre-transplant was 97%. After a median follow-up of 4.4 years the outcome did not differ from that of the historic control, the MCL2 trial with the same treatment except for Zevalin. Overall (OS), event free (EFS), and progression-free survival (PFS) at 4 years were 78, 62 and 71%, respectively. For patients in CRu/PR before transplant who received Zevalin duration of response was shorter than in the CR group. Inferior PFS, EFS- and OS were predicted by PET-positivity pre-transplant and detectable minimal residual disease (MRD) before and after transplant. In conclusion, a positive PET prior to transplant and MRD are strong predictors of outcome. Late intensification with Zevalin may be too late to improve the outcome of patients not in CR before transplant. The study was registered at www.ClinicalTrials.gov (NCT00514475).