IMPORTANCE To achieve the World Health Organization goal of viral hepatitis elimination by 2030, it is important to estimate current rates of chronic hepatitis B (CHB) diagnosis and treatment. OBJECTIVE To provide an accurate accounting of the number of patients with CHB aged 6 years or older who have not yet been diagnosed in the United States. DESIGN, SETTING, AND PARTICIPANTS This cross-sectional study used the commercial US Truven Health MarketScan Database (138 634 154 privately insured individuals in January 2007 to December 2014) to identify patients with CHB diagnosis and the National Health and Nutrition Examination Survey to estimate the actual number of privately insured persons with CHB. Based on sex and age distribution derived from the US Census Bureau, we calculated the total population with CHB and the proportion of those who remained undiagnosed among the 198 073 302 privately insured individuals. Next, we identified diagnosed CHB patients who received 1 or more prescription for CHB medications to calculate the treatment rate for those with severe disease states, such as cirrhosis and hepatocellular carcinoma, that would warrant treatment. Analyses were performed from October 2017 to January 2020. MAIN OUTCOMES AND MEASURES The rate and number of patients with CHB who remained undiagnosed and treatment rates for patients with CHB who have cirrhosis or hepatocellular carcinoma. RESULTS Among the 198 073 302 privately insured individuals (48.55% male; 15.52% aged 6-17 years; 84.48% aged Ն18 years), there were 511 029 (95% CI, 317 733-704 325) individuals with CHB, but only 95 075 of these had been diagnosed, yielding a diagnosis rate of only 18.60% (95% CI, 13.50%-29.92%), meaning that 81.40% (95% CI, 70.08%-86.50%) were undiagnosed. The treatment rates were 34.79% (95% CI, 33.31%-36.27%) for those with cirrhosis and 48.64% (95% CI, 45.59%-51.69%) for those with hepatocellular carcinoma. CONCLUSIONS AND RELEVANCE In this study, only approximately 1 in 5 privately insured patients with CHB had been diagnosed. Only one-third of patients with CHB who had cirrhosis and one-half who had hepatocellular carcinoma received antiviral therapy. Further efforts are needed to improve the current situation of poor connection to care for patients with CHB, especially for those with advanced liver disease.