Lenalidomide in combination with dexamethasone is an effective and well-established treatment of relapsed or refractory multiple myeloma (rrMM) disease. Due to the scarcity of reports assessing benefit and risk of long-term lenalidomide treatment in non-selected rrMM patients, we retrospectively analysed the long-term outcome in patients with rrMM treated with lenalidomide and dexamethasone. Sixty-seven patients (pts) who were treated with lenalidomide/dexamethasone for rrMM in the approved indication from 2007 to 2011 were included in this retrospective, single-centre analysis. Kaplan-Meier survival estimates were compared between total population, patients on lenalidomide for more than 12 months (mo) and patients discontinuing therapy earlier than 12 months. Median overall survival (OS) of the total patient population was 33.2 mo. OS of pts treated beyond 12 mo was 42.9 mo compared to 20.2 mo (p = 0.027) for pts stopping lenalidomide earlier than 12 mo for other reasons than progression disease (PD). OS of pts >12 mo on lenalidomide treatment did not significantly differ between pts who had received previous autologous transplantation, allogeneic transplantation or conventional therapy. Main non-hematologic toxicities were infections of grade 3/4 in 25 % and thrombembolic events of all grades in 18 % of patients. To the best of our knowledge, this is the first report on feasibility and efficacy of long-term lenalidomide treatment in a non-selected patient cohort. OS of pts >12 mo on lenalidomide is superior when compared to pts discontinued earlier for reasons other than PD. Our data confirm the current use of lenalidomide as a continuous long-term treatment strategy.