||The incidence rates of liver cancers, both hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC), are increasing in the U.S. It is possible that the increases are related to common exposures, and if so, similar trends in incidence by gender, age, ethnicity, and calendar period, might exist. To examine this hypothesis, age-specific trends in the incidence of HCC and ICC in the Surveillance, Epidemiology and End Results program (1976-2000) were examined by year of diagnosis and year of birth. Age-period-cohort models were also fit to the data. The incidence of HCC in the most recent time period was twice as high among Black men (8.8/100,000) and women (2.6/100,000) as among White men (4.6/100,000) and women (1.2/100,000). However, between 1976 and 2000, incidence among all four ethnic- and gender-specific groups increased by >90% (White males, 123.2%; White females, 96.8%; Black males, 97.9%; Black females, 91.9%) with young White men experiencing the greatest increases (432%). In contrast, ICC rates were similar for Black (0.93/100,000) and White men (0.92/100,000), but higher for White (0.57/100,000) than Black women (0.39/100,000). Although ICC incidence increased among all groups, the increase was greatest for Black men (138.5%), followed by White men (124.4%), White women (111.1%), and Black women (85.7%) Age-period-cohort analyses of HCC revealed a significant cohort effect among younger men (45-65 years old), but not older men (65-84 years old), suggesting possible differences in etiology. In conclusion, the rates of HCC and ICC approximately doubled between 1976 and 2000. Trends by age, gender, ethnicity, and birth cohort suggest that heterogeneity exists in the factors influencing these rates.