The nuclear factor-kappaB (NF-kappaB) transcription factor system is a crucial component that controls several important biological functions, thus raising the need for mechanisms that ensure the correct termination of its activity. Here, we identify a new phosphorylation/ubiquitination switch in the NF-kappaB network that controls the stability of the transactivating p65 subunit. Tumour necrosis factor-induced phosphorylation of p65 at Ser468 allows binding of COMMD1 and cullin 2, components of a multimeric ubiquitin ligase complex mediating p65 ubiquitination. Mutation of p65 at Ser468 largely prevents p65 ubiquitination and proteasomal degradation. Inducible p65 elimination is restricted to a subset of NF-kappaB target genes such as Icam1. Accordingly, chromatin immunoprecipitation experiments reveal the selective recruitment of Ser468-phosphorylated p65 and COMMD1 to the Icam1 promoter. Phosphorylation of p65 at Ser468 leads to ubiquitin/proteasome-dependent removal of chromatin-bound p65, thus contributing to the selective termination of NF-kappaB-dependent gene expression.