CC-5013-MM-017 is a Phase I, multicenter study to determine the maximum tolerated dose (MTD), safety profile, pharmacokinetics, and preliminary efficacy of lenalidomide with and without dexamethasone in Japanese subjects with previously treated MM. The study will consist of two cohorts: 1) Monotherapy "Maximum Tolerated Dose (MTD) Determination" Cohort; and 2) "Combination Treatment" Cohort.