To demonstrate the generic applicability of CypHer5 pH-sensitive dye, examples of the GPCR subfamilies Gi (d-opioid receptor),Gq(TRHR-1, angiotensin II) and Gs (b-2 adrenergic receptor) were studied. These assays involve the use of CypHer5 labeled anti-VSV-G antibody to detect the VSV-G tagged receptors. Epidermal growth factor receptor (EGFR) plays a central role in the complex signaling pathways involved in cell growth and differentiation and is an example of a non-GPCR that is widely studied. The assay described here uses an exofacial antibody for EGFR that is directly labeled with CypHer5 Mono NHS Ester.