The present study was designed to characterize the blood chemistry, hematology, and lymphocyte subsets in pregnant rhesus monkeys and provide baseline parameters for future studies of reproductive and developmental toxicity and developmental immunotoxicity. Harem-mating was used in 96 female and 16 male rhesus monkeys. Pregnancy was confirmed on gestation day(GD)18 by ultrasound. The blood samples of rhesus monkeys were collected at various times(20 days before pregnancy and GD20, 100 and 150). The analyses of blood chemistry, hematology, and lymphocyte subsets were performed. Copmpared with 20 days before pregnancy, Significant decreases(P < 0.05) were observed in HCT and RBC on GD20, GD150 and in HGB on GD150, Significant increases in NEUT and decreases in LYMPH on GD20 were observed. Significant decreases in ALB from GD20 to GD150 were observed, significant decreases in TP was observed on GD100. Significant increases in mean GLU were observed on GD20 and GD150 during pregnancy. Significant decreases(P < 0.05) in CD20+ subsets on GD100, GD150 and CD4+/CD8+ ratio on GD150 were observed, The significant changes of MCV, MCHC, RDW-SD, MCV, MONO, ALT, AST, GLB, ALP, TBIL, DBIL, IBIL, GGT, CR-S, URIC, TC, TG and CK were observed during the pregnant period, but no biologic change were observed, There were no significant changes in MCH, RDW-CV, MPV, BUN, CD3+, CD4+ and CD8+ during pregnancy. These data provide a database for preclinical study in rhesus monkeys. Physiological anemia, hyperglycemia, and immune suppression may occur in pregnant rhesus monkey which is similar to that found in human, and it is essential to distinguish the physiological changes from the pharmacological effects in reproductive and developmental toxicity and developmental immunotoxicity studies of pharmaceuticals. The present study was designed to characterize the blood chemistry, hematology, and lymphocyte subsets in pregnant rhesus monkeys and provide baseline parameters for future studies of reproductive and developmental toxicity and developmental immunotoxicity. Harem-mating was used in 96 female and 16 male rhesus monkeys. The blood samples of rhesus monkeys were collected at various times (20 days before pregnancy and GD20, 100 and 150). The analyzes of blood chemistry, hematology, and lymphocyte subsets were performed Significant decreases in ALB and GD2050 were observed in GD20, GD150 and in HGB on GD150, Significant decreases in NEUT and decreases in LYMPH on GD20 were observed. Significant decreases in ALB from GD20 Significant increases in TP were observed on GD100. Significant increases in TPU were observed on GD20 and GD150 during pregnancy. Sign GD150 and CD4 + / CD8 + ratio on GD150 were observed, the significant changes of MCV, MCHC, RDW-SD, MCV, MONO, ALT, AST, GLB, ALP, TBIL, There were no significant changes in MCH, RDW-CV, MPV, BUN, CD3 +, CD4 + and CD8 + during pregnancy. These data provide a database for preclinical study in rhesus monkeys. Physiological anemia, hyperglycemia, and immune suppression may occur in pregnant rhesus monkey which is similar to that found in human, and it is essential to distinguish the physiological changes from the pharmacological effects in reproductive and developmental toxicity and developmental immunotoxicity studies of pharmaceuticals.