Tilorone (2,7-bis[(diethylamino)ethoxy]fluoren-9-one) can enhance the humoral immune response of mice to SRBC although Tilorone has no effect on functional activity of splenic B cells in the absence of immunogen. Tilorone does not alter the effective level of T cell help but does seem to alter the level of effective suppression. Tilorone seems to be an adjuvant only in the sense of removing a normal homeostatic control mechanism, perhaps suppressor T cells.