In 1969, Joubert et al. studied a family where four of six children had a severe clinical condition with episodic alternate hyperpnoea and apnoea, hypotonia, ataxia, psychomotor delay, and abnormal ocular movements. Two of the four had agenesis of the posterior-inferior part of the cerebellar vermis and two had complete agenesis of the vermis. We report a 5-month-old girl with Joubert syndrome in whom MRI shows both features typical of this condition and associated corpus callosum agenesis. To our knowledge, complete callosal agenesis has been infrequently reported in children with Joubert syndrome; consequently, it might be regarded as a casual finding. Nevertheless, the hypothesis of a developmental abnormality of midline structures extended to the supratentorial compartment is rather attractive.