Human CD56^bright natural killer (NK) cells possess little or no killer immunoglobulin-like receptors (KIRs), high interferon-γ (IFN-γ) production, but little cytotoxicity. CD56^dim NK cells have high KIR expression, produce little IFN-γ, yet display high cytotoxicity. We hypothesized that, if human NK maturation progresses from a CD56^bright to a CD56^dim phenotype, an intermediary NK cell must exist, which demonstrates more functional overlap than these 2 subsets, and we used CD94 expression to test our hypothesis. CD94^highCD56^dim NK cells express CD62L, CD2, and KIR at levels between CD56^bright and CD94^lowCD56^dim NK cells. CD94^highCD56^dim NK cells produce less monokine-induced IFN-γ than CD56^bright NK cells but much more than CD94^lowCD56^dim NK cells because of differential interleukin-12–mediated STAT4 phosphorylation. CD94^highCD56^dim NK cells possess a higher level of granzyme B and perforin expression and CD94-mediated redirected killing than CD56^bright NK cells but lower than CD94^lowCD56^dim NK cells. Collectively, our data suggest that the density of CD94 surface expression on CD56^dim NK cells identifies a functional and likely developmental intermediary between CD56^bright and CD94^lowCD56^dim NK cells. This supports the notion that, in vivo, human CD56^bright NK cells progress through a continuum of differentiation that ends with a CD94^lowCD56^dim phenotype.