During the conduct of a long-term toxicity/reproduction study using rhesus monkeys (Macaca mulatta), periodic hematologic and serum biochemical analyses were undertaken on blood obtained from 15 untreated (vehicle control) adult female monkeys over a period of 3 yr, 20 untreated adult males over a period of 6 yr, and 9 infants (5 male, 4 female, whose dams were the vehicle control females) from 12 wk through 2 yr of age. All samples were obtained by femoral puncture. To facilitate handling, ketamine hydrochloride (Ket.HCl) was administered to the males, and for some of the later infant samplings. Complete blood cell counts were performed using electronic cell counters, while reticulocyte counts and leukocyte differentials were assessed manually. The serum biochemistry analyses were performed with automated analyzers. These data were obtained as part of a health monitoring program, with medians and 2.5 to 97.5 percentiles for each parameter indicated. Some monitored parameters were found to be affected by the type of equipment used and by the use of Ket.HCl.