Objective: To investigate the clinical features in 44 patients with acute disseminated encephalomyelitis (ADEM). Methods: Consecutive ADEM patients admitted to Neurology Department of the Third Affiliated Hospital of Sun yat-sen University during August 2009 to July 2014 were enrolled.Clinical and laboratory data of the patients were reviewed and analyzed. Results: Forty-four patients with ADEM based on the 2012 criteria were recruited, including 23 male and 21 female; 9 children, 11 teenagers and 24 adults.There were 23 monophasic ADEM (23/44, 52%) and 21 multiphasic ADEM (21/44, 48%). Fourteen patients (31.8%) had definite incentive factors within 2 weeks preceding the disease onset.The commonest presenting symptoms were fever (20/44, 45%), mental disorder (18/44, 41%), disturbance of consciousness (17/44, 39%) and seizure (12/44, 27%). The average EDSS score was (4.3±1.3), and the average mRS score was (2.7±0.9). Abnormal autoimmune antibodies were detected in 10 patients.Two patients were positive for NMO-IgG, and three patients were positive for oligoclonal bands.On MRI scanning, small lesions were observed in 18 of 44 patients (18/44, 41%); large confluent white matter lesions in 10 patients (10/44, 23%); symmetric bithalamic involvement in 12 patients (12/44, 27%). Patients were mainly treated with intravenous corticosteroids (40/44, 90.9%) and immunoglobulin G ( 13/44, 29.5%) in acute phase.Regular follow-up performed in 29 patients (65.9%), and the average follow-up time was (4.2±2.3) year.A monophasic course was found in 10 patients, and multiphasic course in 19 patients.After (2.5±2.3) years, patients with multiphasic ADEM experienced their first clinical relapse, and the relapse frequency was (3.3±1.4). The average EDSS score was (3.9±2.2), and the mRS score was (2.2±1.3) in their latest relapse.In follow-up MRI for (5.3±1.9) years, lesions in 18 patients (62.1%) were partially ameliorated, while 6 patients (20.7%) persisted, and new lesions appeared in 5 patients (17.2%). For the 13 multiphasic patients with regular treatment, intravenous corticosteroids (13/13, 100.0%) and immunoglobulin G (7/13, 53.8%) were still important treatments in the acute phase, while oral steroids (12/13, 92.3%) plus immunosuppressants including azathioprine, tacrolimus, cyclosporine and rituximab were chosen in the remission phase. Conclusions: ADEM is not uncommon in adults, presenting with multiphasic course, encephalopathy features and disseminated lesions on MRI.As it shows very heterogeneous characteristics, ADEM is best viewed as a "syndrome" rather than a specific disorder.