The Marshall-Smith syndrome is characterised by overgrowth, accelerated skeletal maturation, and dysmorphic facial features, often associated with mental retardation of variable degree. Most of the reported patients died in the first three years of life mainly because of respiratory problems. We describe a 5 year old patient with this rare syndrome, who has optic atrophy and agenesis of the corpus callosum, but has no respiratory problems so far. This observation underlines the clinical variability of the Marshall-Smith syndrome and indicates that life expectancy may be prolonged.