Monoclonal antibodies have proved useful in detecting antigenic variation at single determinant sites on complex antigens, a fact which seems to have engendered a common misperception that a monoclonal antibody is necessarily a "monospecific" agent. Yet there exists considerable evidence that individual antibody molecules are multispecific in their binding capabilities, and that the amount of functional and genetic redundancy in mammalian immune systems may be quite large. The implications of this data for the future of monoclonal antibodies are emphasized, along with a brief review of present progress toward human monoclonal antibodies.