Background: ERBB2 (HER2) genomic alterations (GA) are evolving therapy taregets in metastatc coorectal cancer (mCRC). Methods: Hybrid capture based comprehensive genomic profiling (CGP) was performed on 8874 (9.6%) mCRC including both colonic adenocarcinomas (7587 cases; 85%) and rectal adenocarcinomas (1287 cases, 15%) Tumor mutational burden (TMB) was calculated from a minimum of 1.2 Mb of sequenced DNA. Results:ERBB2 amplifications or a short variant (SV) alterations or both were found in 433 (4.9%) of the total mCRC. 195 (45%) of the ERBB2 positive mCRC were female and 238 (55%) were male. Median age was 54 years (range 22 to 88 years). The most frequently co-altered genes were SV GA in TP53 (82%), APC (70%), KRAS (26%), SMAD4 (15%) and PIK3CA (13%). Clinically relevant GA significantly under-represented in ERBB2-altered CRC included significantly reduced GA in KRAS at 26% (p = 0.001) and BRAF at 4% (p = 0.003) as well as other kinases at 1% including EGFR, KIT, MET and RET. The frequency of TMB at > 10 mut/Mb (p < 0.0001), but at > 20 mut/Mb mCRC cases demonstrated virtually the same results regardless to ERBB2 status at a frequency of x%. The overall ERBB2 GA frequency at 5.3% in rectal mCRC is slightly higher than that seen in colonic mCRC at 4.9%, (p = 0.36). The frequency of TMB > 10 mut/Mb in ERBB2 WT mCRC is greater in the colonic mCRC than the rectal mCRC (p < 0.0001 for both comparisons). When > 20 mut/Mb is used as the cut-off, the greater frequency of TMB in colonic mCRC versus rectal mCRC remains significant (p < 0.0001). When the ERBB2altered mCRC cases are evaluated, the greater frequency of TMB > 10 mu/Mb in colonic mCRC versus rectal mCRC remains significant (p = 0.009), but the greater frequency in colonic verses rectal mCRC at the > 20 mut/Mb is not significant (p = 0.37). Conclusions: Although lower than observed in breast and upper gastrointestinal carcinomas where anti-HER2 therapies are approved indications, the frequency of ERBB2 GA in CRC at 4.9% is significant. Importantly, nearly half of CRC ERBB2 alterations are SVs, not detectable by routine IHC and FISH testing. However, the success of anti-HER2 therapies shown here and progress in on-going clinical trials indicates that targeting ERBB2 has potential to become an approved advance in precision therapy for mCRC patients.