The objective was to determine whether Hb declines in healthy elderly men and women and if this influences health-related reference intervals. A representative population sample, comprising 30% of all 70-yr-old subjects in a Swedish city with 420,000 inhabitants (n = 1148, participation rate 85%), was followed at 1-5-yr intervals for 18 yr within a longitudinal population study. Age-related changes in Hb were calculated after exclusion of non-healthy probands and by multivariate analyses in the total study group. Mean Hb declined between age 70 and 88 from 149 to 138 g/L in men (annual decline 0.69 g/L, p = 0.000), and from 139 to 135 g/L in women (annual decline 0.06 g/L, n.s.). Healthy men declined from 152 to 141 g/L (annual decline 0.53 g/L, p = 0.038), for women from 140 to 138 g/L (annual decline 0.05 g/L, n.s.). Age and body mass index correlated, in multivariate analysis, independently to Hb in both men and women, as did variables indicating a non-healthy state. Epidemiological decision limits for anaemia declined for men from 128 to 116 g/L, for women from 118 to 114 g/L. Anaemia, thus defined, occurred in 3.2 to 9.7% of the subjects, whereas 28.3% of the 88-yr-old men had anaemia according to the WHO definition. In conclusion, there is a significant age-related decline in Hb from age 70 to 88 among healthy men, and a less pronounced decline among women. This justifies the use of lower epidemiological decision limits for anaemia of about 115 g/L for both men and women from age 80-82.