Krabbe disease (globoid cell leukodystrophy) is a neurodegenerative disorder that is caused by deficiency of the lysosomal enzyme galactosylceramidase. The resulting accumulation of incompletely metabolized galactocerebroside, which is a component of myelin, leads to progressive white matter disease. The severity of signs and symptoms is partly influenced by the causal mutations and corresponding residual enzyme activity. This review explains how the disease might manifest and discusses methods for diagnosis and staging of the disease process. The current understanding of the mechanisms underlying Krabbe disease is summarized, and therapeutic options--including current and investigational approaches--are outlined.