Objective To explore the growth and developmental parameters and behavioral characteristics of rhesus monkeys during the first year of birth and to establish the background data.Methods A total of 18 (♂=11,♀=7 ) infant rhesus monkeys born from individually caged mothers and with known genetic background and postnatal days were monitored monthly for body weight, body height, head circumference, chest circumference, forelimb length, hind limb length, crown-rump length, tail length and anal-genital distance from postnatal day ( PND) 1 to 360, while hematology, blood chemistry and lymphocyte subsets were examined on PND 28, 175 and 360, and finger maze test was carried out on PND 208.Results The body weight showed linear growth with no significant difference between genders (P>0.05). Except for the anal-genital distance of male infants was significantly greater than that of female infants ( P<0.01 ) , no significant differences were observed between sexes in other morphological parameters.No significant differences of hematology were seen between genders (P >0.05).Compared with that at PND28, TP and BUN were significantly increased (P<0.01) while ALP decreased with no significant difference (P>0.05) at PND 175 and 360.Compared with that at PND28, CD4 +and CD4 +/CD8 +were significantly decreased ( P<0.01) while CD8+significantly increased ( P<0.01) at PND175 and 360.The number of sessions to solve task 2 in learning test was significantly greater than other tasks with females significantly less than males ( P<0.05) .The females had higher correct rate than males in the 2-day random memory test (P<0.05).Conclusions Body weight and morphological parameters show a linear growth.The PND.The RBC, HGB, LYMPH, TP, BUN, ALP, CD4 +, CD8 +and CD4 +/CD8+in hematology, blood chemistry and lymphocyte subsets show relevant changes to the growth and development of organs and systems in infants, which should be highly concerned in drug evaluation.The finger maze test indicates that female infants have better reversal learning and long-term memory than male infants.Background data and behavioral characteristics of infant rhesus monkeys during the first 12 months of birth are established in this study, which provide useful reference and support the evaluation of developmental and reproductive toxicity of drugs in rhesus monkeys.