Infantile-onset megalencephalic leucoencephalopathy (IML) is a recently recognized autosomal recessive white matter disorder. Unlike other megalencephalic leucoencephalopathies, in patients with IML a mild clinical course, a slowly progressive delay in motor development and mild mental deterioration are typical. We report on two affected siblings who have typical clinical and radiological findings of IML. Cranial magnetic resonance imaging showed involvement of the capsula externa, extrema and interna, nucleus dentatus, crus cerebri, periventricular and subcortical white matter. In addition, bilateral cystic changes were determined predominantly in the temporal lobes. There were no clear biochemical or metabolic disturbances. In the present paper, we discuss the clinical and neuroimaging findings of IML.