Twenty-five patients with Duchenne muscular dystrophy, aged between 18 months and 13 years, whose fundamental clinical symptomatology, can be united within three different age groups are presented. These symptoms are in order of frequency: difficulties in walking, general muscular debility and total functional incapacity. Reference to biochemical studies and to studies of healthy carrier mothers, as well as, to electrical, cardiological and phychical studies are made. No differences, with regard to observations made by other authors, except in the C.I. findings on the different mental tests that we carried out are found. Approximately 50% are found to be mentally deficient. Other published theories are quoted herein.