BACKGROUND: Elevated lipoprotein(a) (Lp[a]) is the most common inherited dyslipidemia that is independently and causally associated with increased atherosclerotic cardiovascular disease (ASCVD) risk. However, data from diverse populations with ASCVD are lacking. OBJECTIVE: To evaluate Lp(a) levels in a diverse, contemporary United States (US) population with ASCVD, stratified by race, ethnicity, and sex. METHODS: Lp(a)HERITAGE (NCT03887520) was a multicenter study that estimated the prevalence of elevated Lp(a) in adults (18-80 years) with ASCVD. US participants with Lp(a) measured in nmol/L pre- or post-enrollment were included in this subanalysis. This study was descriptive; therefore, no statistical comparisons were made. RESULTS: Of all US participants, 14% had an Lp(a) measurement pre-enrollment. This subanalysis included 7679 US participants with Lp(a) measurements in nmol/L (80.5% White; 66.4% male; mean age 63.8 years [standard deviation ± 9.7]). Median Lp(a) was > 2.5-fold higher in Black participants (132.0 nmol/L; IQR, 57.1-239.6) vs the overall population (52.1 nmol/L; IQR, 15.7-167.8), and higher in females compared with males (69.4 nmol/L; IQR, 20.1-194.7 vs 45.6 nmol/L; IQR, 14.0-152.6, respectively). Lp(a) levels ≥ 125 nmol/L were more prevalent among Black (52.0%) and female (38.9%) participants vs the overall population (33.3%). CONCLUSION: In US Lp(a)HERITAGE participants, only 14% had an Lp(a) measurement pre-enrollment, despite having ASCVD. One-third of participants demonstrated Lp(a) levels ≥ 125 nmol/L, the threshold for high ASCVD risk, which was higher among Black (1/2) and female (2/5) participants, suggesting a greater need for Lp(a) testing in these groups to inform ASCVD risk mitigation.