Natural killer (NK)–cell recognition of infected or neoplastic cells can induce cytotoxicity and cytokine secretion. So far, it has been difficult to assess the relative contribution of multiple NK-cell activation receptors to cytokine and chemokine production upon target cell recognition. Using Drosophila cells expressing ligands for the NK-cell receptors LFA-1, NKG2D, DNAM-1, 2B4, and CD16, we studied the minimal requirements for secretion by freshly isolated, human NK cells. Target cell stimulation induced secretion of predominately proinflammatory cytokines and chemokines. Release of chemokines MIP-1α, MIP-1β, and RANTES was induced within 1 hour of stimulation, whereas release of TNF-α and IFN-γ occurred later. Engagement of CD16, 2B4, or NKG2D sufficed for chemokine release, whereas induction of TNF-α and IFN-γ required engagement of additional receptors. Remarkably, our results revealed that, upon target cell recognition, CD56^dim NK cells were more prominent cytokine and chemokine producers than CD56^bright NK cells. The present data demonstrate how specific target cell ligands dictate qualitative and temporal aspects of NK-cell cytokine and chemokine responses. Conceptually, the results point to CD56^dim NK cells as an important source of cytokines and chemokines upon recognition of aberrant cells, producing graded responses depending on the multiplicity of activating receptors engaged.