The Adult Health Study (AHS) is a longitudinal study that has included biennial blood pressure measurements since 1958. In the present study, we applied the mixed effects model for serially measured data on the AHS population to (1) examine age-related changes in blood pressure and (2) detect possible radiation effects. The estimated longitudinal model of systolic blood pressure (SBP) depicted a linear increase from 30 to 80 years of age for both sexes. The diastolic blood pressure (DBP) rose linearly to about 65 years of age and then leveled off. There were marked differences in the longitudinal trends of DBP among birth cohorts, particularly for men, with higher DBP levels in the younger cohort. The present analysis demonstrated a small but statistically significant effect of ionizing radiation on the longitudinal trends of both SBP and DBP. This phenomenon is compatible with the degenerative effect of ionizing radiation on blood vessels.