Background: There has been a startling rise in the reported incidence of colorectal cancer (CRC) among adolescents and young adults (AYA; ages 15-39 years) in the US.These patients are often diagnosed with advanced stage and have a relatively poor prognosis.Population-based data on disparities and trends in incidence and mortality in this understudied population are lacking. Methods: We used the Centers for Disease Control WONDER cancer statistics database to extract data on annual age-adjusted incidence (AAIR) and mortality (AAMR) rates per 100,000 population for ?colon and rectal cancer? in AYA. We compared AYA statistics with the overall as well as the non-AYA population (40-85 years). Sex and race comparisons were analyzed. Variations in AAIR and AAMR over time, assessed with Joinpoint regression modelling (Joinpoint regression program 4.9.1.0), were expressed as estimated average annual percentage change (AAPC). Comparisons were reported using average annual percentage change difference (AAPCD). Results: 83,371 cases of EOCRC were reported between 1999-2019. We recorded an increase in AAIR of EOCRC (AAPC 2.9, p < 0.001). We noted a concomitant decline in AAIR of CRC overall (AAPC -2.4, P < 0.001) and among the non-AYA population (AAPC -2.4, p < 0.001). Subgroup comparisons showed statistically significant differences in AAIR of EOCRC for females vs males (AAPCD 0.6, p = 0.04), Whites vs Blacks (AAPCD 1.8, p < 0.001), and White females vs White males (AAPCD 0.6, p = 0.02) [table]. AAMR increased for EOCRC over the study period (AAPC 0.8, p = 0.001), as opposed to a decline in AAMR of CRC overall (AAPC -2.5, p < 0.001) and among the non-AYA population (AAPC -2.5, p < 0.001). The increase in AAMR of EOCRC was similar among males and females (AAPCD 0.3, p = 0.351), but higher among Whites vs Blacks (AAPCD 1.1, p = 0.007). Conclusions: This analysis from a large population-level database shows an increasing trend in incidence and mortality of EOCRC in the US, despite a concomitant decline in the incidence and mortality of CRC overall. The incidence appears to be rising more rapidly among females, particularly White females. Both incidence and mortality of EOCRC appear to be rising more rapidly among Whites compared with Blacks. Our analysis underscores the critical need to develop strategies to identify high-risk AYA populations who may benefit from more aggressive CRC screening and prevention interventions.