Spinal muscular atrophy, type I-III and Duchenne muscular dystrophy belong to the most frequent neuromuscular diseases in children. The purpose of this work was to determine the incidence of these two diseases in liveborn children in the years 1975 to 1989 in the south part of middle Slovakia. The common incidence of all three types of spinal muscular atrophy was 1 in 5631 liveborn children (most frequent was the Werdnig-Hoffmann disease, type I--1 in 12,286). This fact confirms, that this disease belongs to the most frequent autosomal recessive diseases in children of our region too. The incidence of Duchenne muscular dystrophy was 1 in 4827 liveborn boys. The figure is in the range of the published data of the incidence of this disease. The deletion in the dystrofin gene was proved in 70% of affected boys. (Tab. 3, Fig. 1, Ref. 24).