RNase H2 is a holoenzyme comprising 3 subunits (ribonuclease H2 subunits A, B, and C) that cleaves RNA:DNA hybrids and removes misincorporated ribonucleotides from genomic DNA via ribonucleotide excision repair. Ribonucleotide incorporation by eukaryotic DNA polymerases occurs during every round of genome duplication and produces the most frequent type of naturally occurring DNA lesion. We investigated whether intestinal epithelial proliferation requires RNase H2 function and whether RNase H2 activity is disrupted during intestinal carcinogenesis.