We have seen a notable increase in the application of PD-1/PD-L1 inhibitors for the treatment of several solid and hematogenous malignancies including metastatic melanoma, non-small-cell lung cancer and lymphoma to name a few. The need for biomarkers for identification of a suitable patient population for this type of therapy is now pressing. While specific biomarker assays have been developed for these checkpoint inhibitors based on their respective epitopes, the available studies suggested the clinical utility of these biomarker assays is for response stratification and not patient selection. Further improvement in assay development is needed to utilize this type of assay in identification of ideal patient population for this therapy.