Multiple relationships have been noted between DNA repair and transcription in both prokaryotic and eukaryotic cells. First, in both prokaryotes and eukaryotes nucleotide excision repair of the template strand of transcriptionally active regions of the genome is faster than in the coding strand. In prokaryotes the biochemical basis for this kinetic difference appears to be related to the specific coupling of repair to arrested transcription by RNA polymerase. The biochemical basis for strand-specific repair in eukaryotes is unknown. Second, in eukaryotes some or all of the subunits of transcription factor IIH (TFIIH) are required for nucleotide excision repair. The biological significance of this dual function of TFIIH proteins is not obvious. Finally, there are indications that the genes CSA and CSB, which are implicated in the human hereditary disease Cockayne syndrome, may have a role in transcription.