The changes in the haematology and clinical biochemistry associated with the different stages of the menstrual cycle, gestation and lactation in the baboon (Papio hamadryas) were evaluated in a prospective longitudinal study. Serial EDTA and heparin blood samples were collected from 12 baboons. Haemoglobin concentration, haematorcrit, red blood cell and white blood cell counts were decreased in the luteal compared to the follicular phase (PPPPP<0.01) in gestation compared to the phases of the menstrual cycle and lactation. By 1 week post partum, all parameters except haemaglobin had returned to pre‐conception levels.