This national, open-label study is designed to give complementary efficacy, safety and patient reported outcomes (PROs) data in participants with active relapsing forms of MS. Participants will receive a maximum of 2 treatment cycles of ocrelizumab infusions: an initial dose of two 300 milligram (mg) infusions separated by 14 days followed by one single infusion of 600 mg ocrelizumab 24 weeks after the first infusion. Disease activity is determined by clinical relapses and/or Magnetic Resonance Imaging (MRI) activity.

Inclusion Criteria:

• Age >/=18 years at screening
• Patients with relapsing forms of multiple sclerosis (RMS) with active disease defined by clinical or imaging features: (i) at least one clinical relapse over a 6-month period prior to screening; (ii) AND/OR at least one T1 gadolinium-enhancing lesion or new and/or enlarging T2 lesion as detected by brain Magnetic Resonance Imaging (MRI) performed over a 3 months period prior to screening with no change of Disease-Modifying Treatment(s) (DMT) compared to a previous MRI performed within 24 months before screening
• For women of childbearing potential: agreement to use an acceptable birth control method during the treatment period and for at least 12 months after the last dose of ocrelizumab
• Participants should be beneficiary of healthcare coverage under the social security system

Exclusion Criteria:

• Diagnosis of primary progressive MS
• Inability to complete an MRI (contraindications for MRI include but are not restricted to weight ≥140 kg, pacemaker, cochlear implants, presence of foreign substances in the eye, intracranial vascular clips, surgery within 6 weeks of entry into the study, coronary stent implanted within 8 weeks prior to the time of the intended MRI, etc…)
• Gadolinium intolerance
• History of ischemic cerebrovascular disorders (e.g., stroke, transient ischemic attack) or ischemia of the spinal cord
• History or known presence of central nervous system (CNS) or spinal cord tumor (e.g., meningioma, glioma)
• History or known presence of potential metabolic causes of myelopathy (e.g., untreated vitamin B12 deficiency)
• History or known presence of infectious causes of myelopathy (e.g., syphilis, Lyme disease, human T-lymphotropic virus 1 (HTLV-1), herpes zoster myelopathy)
• History of genetically inherited progressive CNS degenerative disorder (e.g., hereditary paraparesis; MELAS [mitochondrial myopathy, encephalopathy, lactic acidosis, stroke] syndrome)
• Neuromyelitis optica
• History or known presence of systemic autoimmune disorders potentially causing progressive neurologic disease (e.g., lupus, anti-phospholipid antibody syndrome, Sjogren's syndrome, Behçet's disease, sarcoidosis)
• History of severe, clinically significant brain or spinal cord trauma (e.g., cerebral contusion, spinal cord compression)
• Vulnerable patients (Patient referred to in Articles L. 1121-5 to L. 1121-8 and L. 1122-1-2 of the French Public Health Code)