BackgroundThe cynomolgus monkey (Macaca fascicularis) has been increasingly used in biomedical research, making knowledge of its blood-based parameters essential to support the selection of healthy subjects and its use in preclinical research. As age and sex affect these blood-based parameters, it is important to establish baseline indices for these parameters on an age and sex basis and determine the effects of age and sex on these indices.MethodsA total of 917 cynomolgus monkeys (374 males and 543 females) were selected and segregated by age (five groups) and sex. A total of 30 hematological and 22 biochemical parameters were measured, and the effects of age and sex were analyzed.ResultsBaseline indices for hematological and biochemical parameters were separately established by age and sex. Significant effects by age, sex, and age-sex interaction were observed in a number of blood parameters. In the 49–60 months and 61–72 months age groups, red blood cell count, hemoglobulin, and hematocrit showed significantly lower values (P<0.01) in females than males. Serum alkaline phosphatase varied with age in both sexes (P<0.01) and was significantly higher in females than males (P<0.05) in the groups aged 13–24 months and 25–36 months; however, in the three groups aged over 25–36 months, serum alkaline phosphatase was significantly lower in females than males (P<0.01). Creatinine concentration increased with age (P<0.01) in all age groups; specifically in the groups aged 49–60 months and 61–72 months, creatinine was significantly higher (P<0.01) in males than females. Total protein and globulin both increased with age (P<0.01).ConclusionThe baseline values of hematological and biochemical parameters reported herein establish reference indices of blood-based parameters in the cynomolgus monkey by age and sex, thereby aiding researchers in selecting healthy subjects and evaluating preclinical studies using this species.