Introduction: In this article, we report the data regarding treatment adherence of a group of patients with multiple sclerosis (MS) and relapsing--remitting or secondary progressive disease who were followed in the MS outpatient clinic of Bozyaka Education and Research Hospital, Izmir. Methods: We collected the demographic data of 219 patients with MS who were treated with immunomodulatory drugs and the documentary data on the disease characteristics from the patient' files. Each patient was provided a detailed questionnaire regarding treatment adherence in addition to the Beck depression scale (BDS) and Paced Auditory Serial Addition Test (PASAT). Nonadherence was defined as the discontinuation of the drug, i.e., more than one dose a month for intramuscular interferon, six doses a month for glatiramer acetate, and four doses a month for subcutaneous interferons. Statistical analyses were performed using Medcalc statistics package. For those parameters with an even distribution, the paired samples t-test was used to compare the results. Results: Of the 219 [183 relapsing remitting multiple sclerosis (RRMS) and 36 secondary progressive multiple sclerosis (SPMS)] patients included in the study, 143 patients were women and 76 were men. The mean age of the patients was 40.77±10.36 years. The mean expanded disability status scale (EDSS) score was 2.90±1.88, and mean annualized attack rate (ARR) was .65±.55. Of the 219 patients, 75.1% continued the immunomodulatory treatment. Thirty-three patients in the RRMS group and 23 patients in the SPMS group abandoned the immunomodulatory treatment. Treatment adherences were similar between patients with RRMS and SPMS (53%). Adherence revealed no correlation with age, ARR, PASAT score, and disease duration. However, higher EDSS and depression scores had significant positive correlation with adherence. Moreover, treatment adherence was noted to be lower in the group with higher education levels. Treatment discontinuation did not correlate with age, ARR, BDS, or PASAT scores. The disease duration and EDSS scores were found to be significantly correlated with treatment discontinuation. Conclusion: In this extensively followed up patients' group with multiple sclerosis, the ones with extended disease duration, higher disability, and more educated had higher rates of treatment discontinuation and lower levels of treatment adherence. The patient-reported outcomes and welldocumented treatment adherence data will contribute to the neurologists' understanding of the patients' inclinations regarding the injectable treatments and help in better management of the immunomodulatory treatments. [ABSTRACT FROM AUTHOR]