BACKGROUND: Recent data indicate that insulin-like growth factor-1 (IGF-1) can cross the blood-brain barrier when bound to binding proteins. IGF-1 is very important for early brain development, myelination and survival of cerebellar neurons. It is antiapoptotic and is important for synaptic development. The aim of this study was to identify neurological conditions with low CNS IGF-1. METHODS: Levels of CSF IGF-1 were determined by radio-immunoassay (Mediagnost, Tubingen, Germany). RESULTS: Levels of CSF IGF-1 were low in some progressive diseases of white matter and the cerebellum. In some other diseases not involving cerebellum or white matter, CSF IGF-1 was normal. CONCLUSIONS: Our findings might pave the way for rational therapy in patients with neurodegeneration. Patients with low CNS IGF-1 might be candidates for IGF-1 therapy.