Since its introduction to North America in 1999, human infection with West Nile virus (WNV) has resulted in considerable acute morbidity and mortality. Although the ongoing epidemic has resulted in a great increase in our understanding of the acute clinical features of human illness and helped to define associated clinical syndromes, far less is known about potential long-term clinical and functional sequelae. Several recent assessments, however, suggest that patients--even those with apparently mild cases of acute disease--frequently have subjective, somatic complaints following WNV infection. Persistent movement disorders, cognitive complaints, and functional disability may occur after West Nile neuroinvasive disease. West Nile poliomyelitis may result in limb weakness and ongoing morbidity that is likely to be long term. Although further assessment is needed, the long-term neurological and functional sequelae of WNV infection are likely to represent a considerable source of morbidity in patients long after their recovery from acute illness.