OBJECTIVES The phase III trial AVOREN demonstrated that BEV + interferon-alpha2a (IFN) prolongs progression-free survival compared with IFN + placebo in patients with untreated mRCC [Escudier, Lancet 2007]. The protocol specified that the recommended dose of IFN (9MIU 3x/week) could be lowered to 6 or 3MIU for grade ≥3 adverse events (AEs) attributable to IFN or other investigator-defined reasons. A retrospective analysis of AVOREN showed that lower-dose (LD) IFN in combination with BEV improves tolerability and maintains clinical benefit [Melichar, Ann Oncol 2008]. We report here the costs of managing side effects of BEV + LD IFN compared with BEV + IFN and sunitinib. METHODS A linear decision analytic model was developed to assess the management costs of all-grade and grade 3/4 AEs for BEV + LD IFN from the perspective of healthcare purchasers in Germany, France and UK. Data sources included published cost literature and clinical trials, official price/tariff lists and country-specific cost databases. RESULTS The total side-effect management costs for BEV + LD IFN were €908, €1,381 and €703 in Germany, France and UK, respectively. The use of BEV + LD IFN provides reduced management costs per patient of €616, €576 and €606, respectively, compared with BEV + IFN, and €1,286, €3,746 and €1,647, respectively, compared with sunitinib. The main drivers for sunitinib costs were thrombocytopenia, neutropenia and lymphopenia compared with fatigue/asthenia, proteinuria and anaemia for BEV + LD IFN. CONCLUSIONS Costs of managing the side effects of sunitinib treatment are greater than those for BEV + IFN in Germany, France and UK [Mickisch, ASCO 2008]. The present analysis shows that combining BEV with LD IFN is associated with the lowest side effect management costs. The tolerability profiles and associated management costs of agents used in mRCC may therefore influence selection of therapy.