Objective: To assess the compliance, satisfaction and adverse effects of immunomodulating drugs in a German multiple sclerosis (MS) population. Research design and methods: A standardised, anonymous questionnaire was sent to the 1985 members with MS of the Berlin section of the German Multiple Sclerosis Association. Patients were questioned with regards to sociodemographic data, MS-related topics, therapy, adverse effects and compliance. The response rate was 51.1%, from which 681 patients were selected who were experienced in therapy with interferon beta 1a or 1b or glatiramer acetate. Results: Most participants were treated with beta-interferons and only one-third with glatiramer acetate. Patients were moderately satisfied with their medication. Approximately 75.5% of patients had used the medication for longer than 2 years, especially those with a relapsing-remitting course (RRMS). Around one-third of all participants had their immunomodulating drug changed, mostly only once. The main reasons for discontinuation of the therapy were adverse effects, physician's recommendation and lack of treatment effect. Mood-related adverse effects (e.g., depression), fever and pain were perceived as most disturbing. Regression analysis revealed that dependence on a wheelchair and a secondary progressive course predicted a low compliance to treatment. Conclusion: Treating MS is a challenge and to positively influence the course of the disease it is necessary to administer medication in a constant manner. Our data showed a moderate compliance and satisfaction with the immunomodulating medication. Adverse effects and perceived lack of treatment effect were reasons for discontinuation of therapy. To increase compliance and satisfaction with treatment, adequate information about MS, the therapeutic options, handling of medication, side-effects and their management are necessary. Additionally, realistic therapeutic aims should be discussed with the patients.