This report describes the activity of transferable suppressor T cells (Ts) generated in vivo in response to minor alloantigens. These Ts cells are antigen specific in both primary and secondary in vivo cytotoxic T lymphocyte responses to minor alloantigens and are the result of a host response rather than of a graft-vs.-host reaction. The Ts cells are produced soon after immunization and their activity is transient. They act via "linked recognition", since they can suppress the cytotoxic T lymphocyte response to noncross-reactive minor antigens, but only if these are presented on the same antigenic cell. A model for dominant low responsiveness in (high X low responder)F1 animals is proposed, whereby Ts cells, activated via the low responder allele, work by linked recognition to suppress helper cells activated via the high responder allele.