The aim of the study was to analyze the rate and direction of changes with age in selected biological traits as well as evaluate their association with lifespan in the Polish population, separately for both sexes. Two types of materials were used in the research: 1) longitudinal sample which comprised 142 persons, including 68 men and 74 women, all were examined for 25 years, starting from age 45; 2) cross-sectional sample which was made up of 223 persons, including 111 men and 112 women. During adulthood and in old age, the research subjects lived for many years in the identical and good environmental conditions, which undoubtedly boosts the value of the study samples. Data on: body height and weight, BMI, complete blood cell count, hemoglobin concentration, hematocrit value, color index, blood glucose level, bilirubin level, thymol turbidity test value, urine specific gravity and pH, systolic and diastolic blood pressure, heart rate, ESR, and body temperature, were analyzed statistically. Taller and slimmer individuals tended to live longer. Similarly, subjects with lower systolic blood pressure (SBP) and lower body temperature had higher age at death. We found that lower blood glucose level and higher bilirubin values were genuine and strong predictors of longevity for men only, whereas higher hemoglobin concentration, higher values of color index, increased absolute granulocyte count (AGC), slighlty elevated lymphocyte count, lower monocyte count as well as total leucocyte count (TLC), lower ESR, and lower thymol turbidity test values were all associated with extended lifespan in women only. Body weight, BMI, bilirubin level, and ESR significantly increased with age in both sexes. Monocyte count rose only in men, whilst red blood cell count, systolic blood pressure, and body temperature increased solely in women. Body height and color index decreased with age in men and women, whilst urine specific gravity diminished with age in women only. We also demonstrated significant U-shaped changes with age in white blood cell count and AGC in both sexes. The same pattern of changes with age was observed for blood glucose level in men as well as band cell count and monocyte count in women. The inverted U-shaped pattern of changes with aging was found for hematocrit value in both sexes, whereas this model proved fitting for diastolic blood pressure in men only.