Glucose-galactose malabsorption (GGM) is an autosomal recessive disease caused by mutations in the Na(+)/glucose cotransporter gene SLC5A1 (OMIM 182380, phenotype number 606824). Patients with GGM present with neonatal onset of severe life-threatening diarrhoea and dehydration. We describe a 5-day-old girl with the typical clinical course of GGM. Our clinical diagnosis was confirmed by an abnormal chromatography of the stool and normal small bowel biopsies. Mutation analysis revealed a novel, homozygous deletion within exon 10 of the SLC5A1 gene, i.e. c.1107_1109 del AGT.