Some blood values of 86 lesser mouse lemurs (Microcebus murinus) maintained in captivity are presented. These are comparable with those of other prosimians: PCV 51.7%, RBC 9.2 × 106/mm3, MCV 57.5 μm3, WBC 12,900/mm3, lymphocytes 59.7%, neutrophils 30.7%, monocytes 4.8%, eosinophils 4.2%, basophils 0.6%. We noted no significant difference between the sexes except that the percentage of lymphocytes was slightly lower in the females (with a corresponding percentage of neutrophils slightly higher). The lymphocyte:neutrophil ratio decreases with age, particularly in young animals; the hematocrit does not vary in adult