The pathogenetic mechanisms of the central nervous system (CNS) problems associated with Langerhans cell histiocytosis (LCH) are not well established. Effective treatment strategies for these CNS complications are not yet available, while diabetes insipidus, also associated with LCH, can be managed effectively. Three Japanese boys with LCH who developed cerebellar ataxia were evaluated. Similar pediatric cases from the literature are also discussed. All three patients initially developed multifocal LCH lesions during early childhood (age <3 years) that responded well to chemotherapy; however, two of the three patients later developed diabetes insipidus. Ataxia, associated with mild developmental delay, was noted in the patients between the ages of 4 to 8 years. Analysis of these three cases, along with previously reported cases, indicates that the median age of onset of LCH was 2.5 (range 0.1-6.5) years and the median age of onset of cerebellar lesions/ataxia was 7 (range 3.5-16.5) years. Although the incidence of cerebellar LCH involvement is low, delayed onset of CNS disease must be monitored during follow-up care of pediatric LCH patients. Brain magnetic resonance imaging is strongly recommended for early detection of cerebellar lesions, but it remains to be determined whether there are any therapeutic measures to prevent exacerbation of CNS disease.