We herein provide a comprehensive assessment of magnetic resonance imaging (MRI) outcomes from CLARITY, a 96-week, double-blind study demonstrating significant clinical and MRI improvements in patients with relapsing-remitting multiple sclerosis (RRMS) treated with cladribine tablets. Patients with RRMS were randomized 1:1:1 to annual short-course therapy with cladribine tablets cumulative dose 3.5 or 5.25 mg/kg or placebo. MRI endpoints included mean number of T1 gadolinium-enhancing (Gd+), active T2 and combined unique (CU) lesions/patient/scan. MRI-measured disease activity was significantly reduced in both cladribine tablets groups versus placebo. The proportion of patients with no active lesions at study end was: T1 Gd+ lesions: 86.8 and 91.0 versus 48.3 % (p