Background: Genetic testing for cancer risk has expanded rapidly, with more genes tested. Little is known about test use or pathogenic variant (PV) prevalence among population-based cancer patients. Methods: Women aged ≥20 years, diagnosed with breast or ovarian cancer in 2013-14 and reported to SEER registries covering the entire populations of Georgia and California, were included. Registry data were linked to clinical genetic testing results, performed from 1/1/2012 through 4/30/2016, by 4 laboratories that did nearly all cancer genetic testing in these states. Results: There were 77,085 breast cancer and 6,001 ovarian cancer patients, with almost 30,000 patients of racial groups other than non-Hispanic (NH) White. One-quarter (24.1%) of breast and one-third (30.9%) of ovarian cancer patients had genetic test results. While test use was similar across racial groups for breast cancer, testing in ovarian cancer patients was lower in NH Blacks (21.6%, CI 18.2-25.4%, vs NH Whites: 33.8%, CI 32.3-35.4%). The most prevalent PVs in breast cancer patients were BRCA1 (3.2%), BRCA2 (3.1%), CHEK 2 (1.6%), PALB2 (1.0%), ATM (0.7%), NBN (0.3%) and TP53 (0.3%); and in ovarian cancer patients were BRCA1 (8.7%), BRCA2 (5.8%), CHEK2 (1.4%), BRIP1 (0.9%), MSH2 (0.8%), ATM (0.6%) and RAD51C (0.6%). Racial differences in PVs included BRCA1 (ovarian cancer: NH Whites, 7.2%, CI 5.9-8.8%; Hispanics, 16.1%, CI 11.8-21.2%) and CHEK2 (breast cancer: NH Whites, 2.3%, CI 1.8-2.8%; NH Blacks, 0.2%, CI 0-0.8%). Among those tested for all genes designated by the National Comprehensive Cancer Network as associated with their cancer type (breast: ATM, BRCA1, BRCA2, CDH1, CHEK2, NBN, NF1, PALB2, PTEN, STK11, TP53; ovarian: BRCA1, BRCA2, BRIP1, EPCAM, MLH1, MSH2, MSH6, PMS2, STK11, RAD51C, RAD51D), 7.7% of breast and 14.5% of ovarian cancer patients had a PV. Conclusions: Clinically tested, population-based breast cancer patients and ovarian cancer patients had 8-15% PV prevalence in guideline-designated cancer risk genes. CHEK2 and ATM PVs were relatively prevalent in ovarian cancer patients: this merits further study because CHEK2 and ATM are not known to be ovarian cancer risk genes. Racial testing disparities are targets for improvement.