Nuclear factor-kappa B (NF-κB) is a family of transcription factors that regulate immune responses, cell proliferation, differentiation, and survival. Activity of the NF-κΒ pathway on a cellular level is tightly controlled through various mechanisms, one of which is the ubiquitin-dependent degradation of chromatin-bound NF-κB subunits. In general, the ubiquitination of NF-κB regulates the duration of gene transcription activated in response to inflammatory signals. In this article, we present protocols to examine the in vivo ubiquitination status of RelA, a critical protein of the NF-κB family.