Clinical pathology, including hematology and serum chemistry, is an important indicator ofbiological changes. Animals for inhalation studies are kept in specific chambers and requirehistorical data for accuracy. Age-related characteristics are essential for interpreting experimental results. This study aimed to provide historical clinical pathology data and analyze age-related trends in these parameters. We collected hematological and biochemical parameters from control groups of male and female F344 rats in the 4-, 13-, 26-, and 52-week repeated inhalation toxicity tests. The number of F344 rats from collected control groups were 24, 60, 50, and 25 males and 25, 60, 50, and 25 females in the 4-, 13-, 26-, and 52-week studies, respectively. Mean comparison, correlation analysis and simple linear regression analysis was conducted to reveal age-related trends. Neutrophil count, eosinophil count, neutrophil percentage, monocyte percentage, total protein, albumin, triglyceride, total cholesterol (TCHO) showed increasing trends, whereas lymphocyte count, lymphocyte percent, platelet count, alkaline phosphatase, albumin/globulin ratio, and inorganic phosphate showed decreasing trends in both the mean comparison and regression analyses. TCHO was con-sidered the most affected parameter by aging in both sexes based on statistical results. Inthis study, we presented clinicopathological data from F344 rats for inhalation toxicity studies.We confirmed aging trends in clinicopathological parameters and identified TCHO as theparameter most affected by aging in F344 rats. These results would be helpful for inhalationresearch using F344 rats.