Human natural killer (NK) cells are regulated by a diverse receptor repertoire. This makes multi-color flow cytometry-based approaches highly attractive for detailed phenotypical evaluation of NK cells. Several functional parameters can also be evaluated using this technology. In the present chapter, we demonstrate the applicability of this technology for the analysis of the human killer cell Ig-like receptor (KIR) repertoire. We present an antibody panel allowing simultaneous assessment of the four major inhibitory KIRs and NKG2A. We further provide guidance on how to apply standard operating procedures to multi-color flow cytometry experiments. Finally, we discuss possibilities as well as limitations with the application of multi-color flow cytometry techniques to future studies of human NK cells.