Description: Background Lenalidomide has dual antiangiogenic and immunomodulatory properties and confirmed antitumor activity in hematologic malignancies. A phase II study investigating the safety and efficacy of continuous lenalidomide in recurrent ovarian cancer patients was initiated. Patients and methods Patients with histologically confirmed epithelial ovarian, fallopian tube or primary peritoneal carcinoma, with asymptomatic recurrence 6 months after prior therapy were treated with continuous oral lenalidomide (20 mg/day). The primary end point was to evaluate efficacy according to the rate of disease control at 4 months. Secondary objectives were progression-free survival (PFS) and safety. Results Most of the 45 patients enrolled and treated had serous histology (78%) and a single line of prior chemotherapy (73%). Median platinum-free interval (PFI) was 11.3 months (range 6.9–56.8). Clinical benefit at 4 months was 38% [95% confidence interval (CI) 23% to 53%]. A 59% disease control rate was reported in patients with a PFI 〉12 months versus 24% with PFI of 6–12 months ( P = 0.023). Four patients had RECIST partial responses and 21 had stable disease. CA125 responses were reported in eight patients, including one complete response. Median PFS was 3.4 months (95% CI 2.4–4.4). Most frequent toxicity was hematologic, notably grade 3–4 neutropenia in 29% of patients, along with fatigue (69%), gastrointestinal toxicity (constipation 53%, abdominal pain 49%, diarrhea 38%, nausea/vomiting 36%) and thrombosis (11%). Eight patients withdrew due to related toxicity. Conclusions Lenalidomide shows interesting efficacy in late recurrent ovarian cancer patients. Toxicity was mainly hematologic, gastrointestinal and venous thrombosis. Future studies will evaluate combination of lenalidomide with chemotherapy agents. Clinicaltrials.gov NCT01111903.