Lenalidomide is an oral immunomodulatory drug that has helped improve outcomes in multiple myeloma (MM) patients. Combination lenalidomide and dexamethasone (Len+Dex) has been shown to increase response rates and prolong survival compared with dexamethasone alone in patients with relapsed or refractory MM (RRMM). Clinical benefit may be greatest when Len+Dex is given at first relapse, and continued treatment appears to provide greater depth of response and improved survival outcomes. The most common adverse events associated with Len+Dex are cytopenias, which are predictable and manageable. Len+Dex is associated with an increased risk of venous thromboembolism, which necessitates adequate prophylaxis. The risk of second primary malignancies does not appear to be increased in patients with RRMM treated with lenalidomide-based therapy. Here we review the safety and efficacy of Len+Dex in RRMM, and provide an overview of data from Spain on the use of Len+Dex in RRMM.