Recent clinical studies in multiple sclerosis have provided new data on glatiramer acetate, interferon-beta preparations and natalizumab, which will have important implications for optimising patient care. Once a diagnosis has been made with confidence, early initiation of immunotherapy is warranted because of the presence of continuous inflammatory disease activity. Approval for therapy in patients with a clinically isolated syndrome has been granted to several first-line treatments, and most recently to glatiramer acetate. The utility of systematic frequent MRI monitoring of disease activity and response to therapy is not yet clearly established. Treatment efficacy after initiating therapy at the first demyelinating episode has to be followed carefully and re-evaluated whenever necessary. The occurrence of further relapses, confirmed disability progression or MRI evidence of persistent or aggravated disease activity would be regarded as evidence for an inadequate treatment response. However, limitations of clinical scores in faithfully reflecting disease activity at all times, as well as uncertainties about the discriminatory capacity of surrogate measures such as MRI, need to be clarified before clear-cut recommendations on treatment failure can be advocated. Escalation therapy is reserved for patients presenting with 'aggressive disease', which can be operationally defined as the occurrence of two severe relapses within twelve months, together with either MRI evidence for persistent disease activity or a two-point progression of disability on the EDSS.