Sympathetic neurons from newborn rats, cultured for 1 month or longer in the virtual absence of nonneuronal cells, were capable of regenerating neurites after neuritotomy. Regeneration occurred even after nerve growth factor was withdrawn from the cultures, although it was much less extensive and appeared limited to a few days following neuritotomy. Even after 29 days of nerve growth factor deprivation, reintroduction of the protein prompted a resumption of neurite growth. Possible roles of both nerve growth factor-independent and -dependent components in adult nerve regeneration are discussed.