Several disease-modifying agents (DMAs) are approved for the treatment of multiple sclerosis, including three interferon (IFN)-β products, glatiramer acetate and mitoxantrone. This article reviews the adverse event profiles of these DMAs based on the pivotal phase III trials, and provides practical guidelines for managing adverse effects. In general, the most common adverse events associated with IFNβ therapy are flu-like symptoms, including fever, chills and myalgias, and headache. The flu-like symptoms typically resolve within 24 hours and may be mitigated by over-the-counter anti-inflammatory agents. Adverse events related to glatiramer acetate therapy include injection-site reactions and a systemic reaction consisting of flushing, chest tightness, palpitation, anxiety or dyspnoea. The systemic reaction is transient (30 seconds to 30 minutes) and self-limited. Mitoxantrone may cause nausea, vomiting, alopecia, amenorrhoea and myelosuppression; isolated cases of acute leukaemia and dose-related cardiotoxicity have been reported in the literature. Longer-term tolerability data on mitoxantrone as a treatment for multiple sclerosis are needed. It is important for physicians to counsel patients on DMA-related adverse effects, most of which are transient and of mild-to-moderate severity. Various strategies that can be employed to prevent or manage these adverse effects and lessen their impact on the patient are discussed.