Alterations in production of cytoskeletal protein dystrophin caused by in-frame gene mutations lead to the Becker muscular dystrophy. In this study we analyzed genotype-phenotype correlation in a group of Becker muscular dystrophy patients with deletions affecting the proximal part of dystrophin gene, encompassing exons 3-13. Four patients with deletions affecting N terminal dystrophin domain had early onset and faster progression of the disease, while three patients with deletions in the proximal part of dystrophin's rod domain had a more benign disease course. Our study suggests that proximal gene deletions in Becker muscular dystrophy have various phenotypic effects depending on the affected domain of protein dystrophin.