Becker Muscular Dystrophy is an X-linked recessive inherited disease caused by in frame mutations in the dystrophin gene that lead to the expression of partially functional dystrophin. BMD has been historically underserved as compared to DMD because it was and is still being labeled as a less severe disease than DMD. Hence the limited clinical trials and no FDA approved drugs for BMD except for some corticosteroids use to reduce muscle inflammation and delay onset of cardiomyopathy. Nevertheless, the BMD patients exhibit a heterogenous clinical severity with some patients exhibiting a more DMD-like phenotype at a young age while others exhibiting mild phenotype and live longer. There is no clear understanding of how the mutations correlate with the phenotype in BMD. In this study we aim to define non-invasive urinary biomarkers for monitoring disease progression in BMD. This can eventually be used to assess efficacy of future treatment or help drug development programs for BMD. We hypothesize that urinary proteins associated with muscle damage could serve as tool to assess disease severity in BMD patients. By analyzing urine samples of 49 patients and age matched healthy controls, we identified and validated urinary N-terminal titin fragment as a sensitive biomarker to assess disease severity in BMD.