Lenalidomide is an immunomodulatory drug administered orally in the treatment of multiple myeloma. Some elderly patients require a reduced lenalidomide dose because of comorbidities and/or adverse events. This study investigated the actual dose of lenalidomide in elderly patients, finding that most received reduced (5-10 mg) doses. The most common reasons for dose reduction were renal dysfunction (54% of patients), fatigue (grade ≥3; 20%), hematologic disorder (grade ≥3; 14%), and rash (grade ≥3; 9%). Their median time to progression was 11.8 months and their median overall survival was 39.2 months. The overall response rate was 73%, including 17% with a complete response, 19% with a very good partial response, and 37% with a partial response. These results showed that, contrary to western countries, most patients were treated with a reduced dose of lenalidomide in Japan. However, it is suggested that continued treatment with a tolerable dose may yield favorable outcomes.