Considerable data indicate posttransplant lenalidomide prolongs progression-free survival and probably survival after an autotransplant for plasma cell myeloma (PCM). However, optimal therapy duration is unknown, controversial and differs in the EU and US. We compared outcomes and cost-effectiveness of 3 posttransplant lenalidomide strategies in EU and US settings: (1) none; (2) until failure; and (3) 2-year fixed duration. We used a Markov decision model which included 6 health states and informed by published data. The model estimated the strategy of lenalidomide given to failure achieved 1.06 quality-adjusted life years (QALYs) at costs per QALY gained of €29,232 in the EU and $133,401 in the US settings. Two-year fixed-duration lenalidomide averted €7,286 per QALY gained in the EU setting and saved 0.84 QALYs at $60,835 per QALY gained in the US setting. These extremely divergent costs per QALY in the EU and US settings resulted from large differences in costs of posttransplant lenalidomide and of 2nd-line therapies driven by whether posttransplant failure was on- or off-lenalidomide. In Monte Carlo simulation analyses which allowed us to account for variability of inputs, 2-year fixed-duration lenalidomide remained the preferred strategy for improving health-care sustainability in the EU and US settings.