The ultrastructural and histochemical exploration of histiocytes X done by the means of Concanavalin A (Con A), peanut agglutinin (PNA) and BSPT demonstrate that the plasma membrane of histiocytes X shared some properties with all the other cells and is also specialized. The rod part of the X body has the same properties as the plasma membrane while its vesicular part differs and is closer to the inner membrane system of the cell. In consequence it is suggested that the rod part of the X body is a specialized pathway or shuttle for receptor linked glycoprotein exchanges in highly specialized cells.