The aim of the present report was to estimate the proportion of autosomal recessive (AR) inheritance among families with affected males diagnosed as Duchenne muscular dystrophy (DMD) in which X-linked inheritance could not be confirmed. A total of 470 families was studied: 20 with at least one affected girl with "Duchenne-like" phenotype and 450 with only affected boys. Based on the number of families with at least one affected girl and the number of patients per sibship among these pedigrees, the proportion of families with DMD inherited as an AR trait was estimated at 6.8%. It is also estimated that 2.5-4% of male isolated patients diagnosed as DMD may have the AR form, which could be one possible explanation for the inconsistent results between clinical diagnosis and dystrophin assessment in one case recently reported.