An autopsy case of neoplastic angioendotheliomatosis (NAE) in a 65-year-old male is reported. At autopsy, the paraaortic lymph node was slightly enlarged, and bilateral swelling of adrenal glands was found. Histologically, multifocal proliferation of atypical cells was seen in the sinusoid or in the lumen of blood vessels throughout many organs, but there was little invasion of the parenchyma by these cells. From these findings, it was diagnosed as NAE. Immunohistochemically, these atypical cells showed positive reaction to the antileukocyte common antigen, anti-MB-1, LN-1, and LN-2, and negative reaction to the anti-Ki-1, anti-MT-1, anti-kappa, anti-lambda, and antifactor-VIII-related antigen. These findings showed that the atypical cells of NAE were of B lymphocyte origin.