The term “NK receptors” has been applied to a growing number of cell surface receptors that were initially identified by their expression on NK cells. However, it is becoming increasingly obvious that few or none of the known “NK receptors” are completely restricted in expression to NK cells. For example, many of the inhibitory mouse Ly49 receptors were in fact originally cloned from T cell lines [1],[2], the NKR-PI [3],[4] and CD94/NKG2A receptors are found on subsets of both human and mouse T cells [5]–[7], and KIR have been identified on human T cells [8],[9]. Typically, these “NK receptors” are present on effector or memory T cells, most frequently on γδ-TcR+ T cells or CD8+ T cells, and are rarely observed on naive resting T cells. Thus, the expression of “NK receptors” on T cells implies a role in adaptive, as well as innate, immunity.