Prevalence of progressive muscular dystrophy in 1965 and incidence in Denmark for the period 1965 to 1975 was studied by collection of data from hospital departments, nursery homes and general practitioners. This material was supplemented with information from death certificates and disablement pension records. Total patient group included 445 patients with progressive muscular dystrophy alive January 1st 1965. Prevalence was 69.4 per 10(6) male inhabitants in the Duchenne type, whereas the prevalences in the limb-girdle and facioscapulohumeral types were 36.5 and 18.6 per 10(6) inhabitants, respectively. Incidence was 222 per 10(6) male newborns in the Duchenne type, 66 and 26 per 10(6) newborns for the limb-girdle and the facioscapulohumeral types, respectively. Figures for the Duchenne type are in agreement with previous results. Both prevalence and incidence rates for the limb-girdle and the facioscapulohumeral types exceed published figures by a factor 3 to 6. These high Danish rates seem to reflect the true prevalence and incidence in the less serious types of progressive muscular dystrophy, probably because the Danish health system with free medical care and easy access to specialized hospital departments makes it possible to identify all cases of progressive muscular dystrophy.