Sign languages used in Deaf communities are naturally evolving languages that exhibit the full range of linguistic complexity found in spoken languages. Neurolinguistic studies have helped identify brain regions that are critical for sign language and have documented the dissolution of sign language in cases of sign aphasia. Complementary data from neuroimaging and electrophysiology have confirmed and extended our understanding of the intricacies of the neural systems underlying sign language use. Studies of sign language aphasia have informed the question of hemispheric specialization for human languages, and this characterization has evolved since the advent of cognitive neuroscience methods used to study brain-intact signers. Taken together, these studies provide a privileged avenue for understanding the neural regions that underlie human language abilities.