Molecular mechanisms underlying subarachnoid hemorrhage (SAH)-induced cerebral vasospasm are complex and still partially unknown. Molecular-biological studies and clinical trials support a central role of ion channels, but further detailed studies have to evaluate their exact role during vasospasm following SAH. This chapter focuses on methods and principles of ion channel assessment which includes the wide-spread spectrum of molecular-biological, electrophysiological, immunochemical, and functional methods.