GM1 Gangliosidosis is an autosomal recessive genetic disorder due to deficiency of the lysosome enzyme beta-galactosidase, with consequent tissue accumulation of glycolipids, oligosaccharides, and especially GM1 ganglioside. In the present paper we report the clinical and laboratory findings obtained for eight families starting from eight index cases exhibiting the childhood form of the disease. The total number of cases in these families may be as high as 14, thus causing GM1 gangliosidosis to be the inborn metabolic error most frequently diagnosed in our service. Hypotonia, neuromotor retardation, hepatosplenomegaly, macrocephaly, and hydrocele are some of the most frequent clinical findings. The disease evolves towards convulsions and bronchopneumonia, leading to patient death generally during the first half of the second year of life. The presence of vacuolated lymphocytes, alterations of the lumbar vertebrae, and cherry spots on the retina were observed in almost all patients. When tested for inborn metabolic errors, all patients gave normal results, a fact that may have confused and delayed diagnosis. Diagnosis was made by urine oligosaccharide chromatography and confirmed by beta-galactoside measurement in peripheral blood leukocytes. This method proved to be accurate also for the detection of heterozygotes, which permitted post-mortem diagnosis in two families. The authors speculate that increased fetal loss and tendency towards macrosomy may be possible characteristics of the disease, suggest that testing for vacuolated lymphocytes be used as a screening method, and propose that urine oligosaccharide chromatography be included in the routine screening for inborn metabolic errors.