Van Dyke AL, et al. - Researchers used population-based North American Association of Central Cancer Registries data to study demographic differences in biliary tract cancer (BTC) incidence rates and time trends by anatomic site in the US. For 1999-2013, age-adjusted incidence rates, incidence rate ratios (IRRs), and estimated annual percent changes (eAPCs) by site and demographic group were calculated. They compared IRRs by age group for sites with significant differences in eAPC by age group. Among women and all racial/ethnic groups, a decline in gallbladder cancer (GBC) incidence rates was observed. Increased rates were reported among non-Hispanic blacks. An increase in the GBC rates and decreased GBC rates were observed among 18- to 44-year-olds and among people 45 years old or older, respectively. For younger people vs older people, larger sex and racial/ethnic differences in GBC incidence were observed. A steady increase in intrahepatic cholangiocarcinoma and extrahepatic cholangiocarcinoma rates was observed across sex and racial/ethnic groups during this period. Findings demonstrated increased ampulla of Vater cancer incidence rates among younger adults but not among older adults, however, sex and racial/ethnic IRRs did not differ by age.