STING (stimulator of interferon genes) plays a critical role in the innate immune response, including in viral infection, cancer immunity, and several autoimmune diseases. Here, we present a protocol for detection of STING oligomerization, a critical step in STING activation. We describe steps for expressing STING in HEK293T cells, activating STING by 2'3' cyclic GMP-AMP (cGAMP) treatment, and analyzing STING oligomerization by non-reducing SDS-PAGE and blue native PAGE. This protocol is useful for studies of STING functions, regulation, and dysregulation. For complete details on the use and execution of this protocol, please refer to Liu and Manley.(1).