Progressive telomere shortening with aging was studied in the normal liver tissue of 94 human subjects aged between 0 and 101 years old to determine the rate of telomere loss in 1 year. Telomere length demonstrated accelerated shortening with reduction of 55 base pairs (bp) per year. The mean telomere length in five neonates was 12.9 +/- 2.6 kilobase pairs (kbp), and that in one centenarian was 8.3 kbp. Mean telomere lengths by age group were 13.2 +/- 2.0 kbp (< or = 8 years; 10 subjects), 7.8 +/- 1.9 kbp (40-79 years; 29 subjects), and 7.5 +/- 2.0 kbp (> or = 80 years; 53 subjects), with reduction thus appearing to show slowing on the attainment of middle age. The difference of mean telomere lengths for two groups with or without advanced malignancies of other than liver origin was not significant in the older two groups. Despite the slow turnover of liver tissue, the overall reduction rate of telomere length decrease in 1 year was almost the same as that of digestive tract mucosa, with its very rapid renewal.