A multidisciplinary study was conducted in order to assess dystrophin expression in a large series of mild X-linked muscular dystrophy patients, with well-defined clinical phenotype. Patients (104) were divided in 4 clinical groups, according to clinical severity: asymptomatic (sub-clinical), benign, moderate and severe, Cardiopathy was also assessed, and dilated cardiomyopathy was found in 47% of sub-clinical and benign cases. Myoglobinuria, cramps and myalgia were also associated with a sub-clinical or benign clinical status. Dystrophin immunohistochemical pattern of labelling and dystrophin amount decreased gradually across clinical groups. Our study showed a significative correlation between: (1) dystrophin amount and immunohistochemical score (p < 0.05); (2) dystrophin amount and clinical score (p < 0.05). Therefore, the combined use of these different techniques for prognosis of mild X-linked muscular dystrophy patients is useful. Our study assesses the prevalence of the various disease courses in a large cohort of mild X-linked muscular dystrophy patients. From our series, up to 30% of patients may be either asymptomatic or have sub-clinical changes.