Speech characteristics and the language development in children with Duchenne muscular dystrophy (DMD) were examined. Speech characteristics of 45 boys with DMD were extracted by rating their speech samples based on the acoustic judgement. The impairment of overall intelligibility of speech was noted in 24 of the subjects. The data suggested that the impairment of intelligibility consisted of “voice weakness” and “imprecision of vowel and consonant articulation”, which were considered to be due to the weakness of the related muscles. Poor performance score in the tests of the function of the speech articulators also suggested the weakness of the muscles of respiration, phonation and articulation. In 8 of the subjects, abnormal pattern of tongue articulation was found in which the tip or dorsum of the tongue placed forward. Wechsler Intelligent Scale for Children (WISC) and Illinois Test of Psycholinguistic Abilities were carried out on 24 boys (8 years to llyears-10 months) of the 45. For intellectual function, the subjects presented a considerably low intelligent quotient (FIQ=74.3) in WISC. They obtained higher performance IQ (PIQ=83.3) than verbal IQ (VIQ=70. 8) . In ITPA, the mean score of total PLA (Psycholinguistic Learning Age) was 3 years behind the chronological age and a year behind the metal age. It was considered that language impairment affected all modalities, especially “verbal expression” and “manual expression”.