Importance: Data from the coronavirus disease 2019 (COVID-19) pandemic in the US show large differences in hospitalizations and mortality across race and geography. However, there are limited data on health information, beliefs, and behaviors that might indicate different exposure to risk.

Objective: To determine the association of sociodemographic characteristics with reported incidence, knowledge, and behavior regarding COVID-19 among US adults.

Design, Setting, and Participants: A US national survey study was conducted from March 29 to April 13, 2020, to measure differences in knowledge, beliefs, and behavior about COVID-19. The survey oversampled COVID-19 hotspot areas. The survey was conducted electronically. The criteria for inclusion were age 18 years or older and residence in the US. Data analysis was performed in April 2020.

Main Outcomes and Measures: The main outcomes were incidence, knowledge, and behaviors related to COVID-19 as measured by survey response.

Results: The survey included 5198 individuals (mean [SD] age, 48 [18] years; 2336 men [45%]; 3759 white [72%], 830 [16%] African American, and 609 [12%] Hispanic). The largest differences in COVID-19–related knowledge and behaviors were associated with race/ethnicity, sex, and age, with African American participants, men, and people younger than 55 years showing less knowledge than other groups. African American respondents were 3.5 percentage points (95% CI, 1.5 to 5.5 percentage points; P = .001) more likely than white respondents to report being infected with COVID-19, as were men compared with women (3.2 percentage points; 95% CI, 2.0 to 4.4 percentage points; P < .001). Knowing someone who tested positive for COVID-19 was more common among African American respondents (7.2 percentage points; 95% CI, 3.4 to 10.9 percentage points; P < .001), people younger than 30 years (11.6 percentage points; 95% CI, 7.5 to 15.7 percentage points; P < .001), and people with higher incomes (coefficient on earning ≥$100 000, 12.3 percentage points; 95% CI, 8.7 to 15.8 percentage points; P < .001). Knowledge of potential fomite spread was lower among African American respondents (−9.4 percentage points; 95% CI, −13.1 to −5.7 percentage points; P < .001), Hispanic respondents (−4.8 percentage points; 95% CI, −8.9 to −0.77 percentage points; P = .02), and people younger than 30 years (−10.3 percentage points; 95% CI, −14.1 to −6.5 percentage points; P < .001). Similar gaps were found with respect to knowledge of COVID-19 symptoms and preventive behaviors.

Conclusions and Relevance: In this survey study of US adults, there were gaps in reported incidence of COVID-19 and knowledge regarding its spread and symptoms and social distancing behavior. More effort is needed to increase accurate information and encourage appropriate behaviors among minority communities, men, and younger people.