Glutaric aciduria type I (GA-I) is a rare inherited metabolic disease with increased excretion of glutaric acid and its metabolites. Diagnosis is often delayed until the onset of irreversible neurological deficits.We reviewed the clinical and imaging (US, CT and MRI) findings in six patients with proven GA-I and with emphasis on the early US findings. Coronal and sagittal US images of the brain were obtained through the anterior fontanelle in all patients. CT was obtained in three patients and MRI was obtained in two.Macrocephaly was found in all patients, being present in three children at birth or developing rapidly within the first weeks of life. US showed, in all patients, bilateral symmetrical cyst-like dilatation of the sylvian fissures. Progressive fronto-temporal atrophy developed within the first months. CT and MRI demonstrated fronto-temporal atrophy with lack of opercularisation in all cases and basal ganglia or periventricular hypodensities in three patients.In patients with macrocephaly at birth or rapidly developing within the first weeks of life, US should be performed as the primary imaging modality. Cyst-like bilateral widening of the sylvian fissures is the first sign of GA-I, followed by progressive fronto-temporal and ventricular enlargement. These patients should be screened for GA-I in order to initiate treatment in the asymptomatic stage.