In this study, the tolerability and safety of treatment with pulsed steroids and glatiramer acetate and the occurrence of clinical and radiological activity after natalizumab (NTZ) cessation in multiple sclerosis (MS) patients were assessed. MS patients with NTZ were discontinued after 2 years of treatment, or if adverse events or disease progressed during NTZ. They were offered as alternative treatment 1 g methylprednisolone per month during 3 months followed by daily 20 mcg glatiramer acetate and were prospectively studied. Adverse events, occurrence of immune reconstitution inflammatory syndrome, clinical exacerbations, and gadolinium-enhancing lesions in MRI performed at 3 and 6 months after NTZ cessation were recorded. EDSS change during follow-up was also recorded. A total of 18 MS patients entered the study and were followed up for a mean of 10 months (range 6-18 months). There were no significant adverse events. At month 3, no patient had clinical or radiological disease activity. At month 6, 16.6% of patients had had a relapse and 55.5% of patients showed gadolinium-enhancing lesions in the MRI. After 6 months, 33.3% of patients had a further relapse. There was no IRIS, severe relapses, or significant difference between EDSS at NTZ discontinuation and after follow-up. The alternative treatment with monthly prednisolone followed by GA prevents the development of IRIS, but not the return to previous inflammatory activity, which occurs between 5 and 6 months after NTZ withdrawal.