Current knowledge of infantile spinal muscular atrophies (ISA) is reviewed by analyzing cases seen by the neurology service at Hospital Sant Joan de Déu in Barcelona from 1978 through 1986. The assessment is mainly clinical. The total number of patients is 60, as follows: 24 with severe or type I forms, 24 with intermediate or type II forms and 12 with type III forms. All type I patients presented hypotonia and weakness before age four months and died before the age of two years. DNA genome tests were performed for eight, revealing that four had deletions in the seventh and eighth exons. One patient had a single deletion in exon 7, one had a deletion in the neuronal apoptosis inhibitory protein gene as well as in exon 7. No deletions were detected in two patients. Four type II patients died of respiratory complications. All except one acquired autonomous sedestation. Severe scoliosis presented in 14 patients, with most requiring corsets. Fourteen required arthrodesis of the spinal column by way of Luque's technique. DNA genome studies were performed for 19, revealing that 14 had deletions in both exons 7 and 8. Exon 7 deletion was present in two. Two also had deletions in exon 3, an abnormality known as the "Spanish mutation". Genetic conversion or an equivalent deletion in exon 7 was observed in the remaining patients. Five of the type III patients walked autonomously, although with pelvic balancing and Gower's maneuver upon rising from the floor. Braces were required for walking by four, whereas three walked so precariously that they only achieved partial autonomy inside the home. DNA genome studies were performed in seven, revealing exon 7 and 8 deletions in six patients. Only one presented a partial deletion in exon three.