Thyroid carcinomas with follicular phenotype have demonstrated changing patterns over 30 years (1973-2003) according to data from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute. Papillary carcinomas have significantly increased. They accounted for 74% of all cases of thyroid cancers in 1973 and 87% in 2003. During this period, the incidence rate of papillary carcinoma (including the follicular variant) increased by 189%, the rate of follicular carcinoma remained stable, and the rate of anaplastic carcinoma decreased by 22%. The rate of the follicular variant of papillary carcinoma alone increased by 173%. Thyroid cancer was more common in whites than in blacks and in females more than in males. Papillary carcinomas rapidly increased during adolescence and reached a peak around age 52-56, then declined. Follicular carcinomas increased steadily, but at a lower rate until age 80. After 1988, both papillary and follicular carcinomas, less than 2 cm, increased at the same rate as carcinomas larger than 2 cm. However, papillary carcinomas less than 2 cm were more common. Overall, the 10-year relative survival rate was greater than 90% for blacks and whites with the exception of follicular carcinoma in blacks. The 10-year relative survival rate for anaplastic carcinoma in patients over 40 years of age was 4.7%. The decrease in incidence rate of anaplastic carcinoma may be the result of the successful treatment of papillary and follicular carcinomas.