We analyzed historical control data of clinical pathology testings provided by sixty-seven member companies of the Japan Pharmaceutical Manufacturers Association covering study populations of approximately 7, 000 rats/sex, 5, 000 dogs/sex, and 700 monkeys/sex. This paper assesses the relationship between conditions of sample collection, methods of measurement, etc. and potential factors contributing to variations in reference data, based on weighted means and standard deviations there of derived from data for rats, dogs and monkeys for those parameters measured using methods most common to the participating facilities. Parameters included erythrocyte count (RBC), hematocrit (Ht), hemoglobin concentration (Hb), reticulocyte count (Rt), platelet count, total leukocyte count (WBC), differential leukocyte count (%WBC), coagulation time (activated partial thromboplastin time: ARTT, prothrombin time: PT), and serum/plasma levels of GOT, GPT, ALP, LDH, glucose, cholesterol, triglycerides (TG), total protein, albumin, urea nitrogen (UN), creatinine, sodium (Na), potassium (K), calcium (Ca), chloride (Cl), inorganic phosphorus (Ip), and CPK. Analyses of the data revealed species differences in RBC, Ht, Rt, platelet count, WBC, %WBC, ALP, LDH, glucose, cholesterol, TG, total protein, UN, creatinine, Ca, Ip, and CPK. There were strain differences in rats in platelet count, WBC, GOT, ALP, UN, creatinine, and CPK. Sex differences were noted for Hb, Ht, WBC, ALP, glucose, cholesterol, TG, total protein, A/G ratio, UN, and Ip. Age differences were observed with RBC, Hb, Ht, Rt, %WBC, GOT, GPT, ALP, LDH, cholesterol, TG, total protein, Ip, and Ip, and CPK, ARTT, PT, ALP, glucose, TG, and UN were found to be subject to the influence of fasting/feeding. In rats, Ht, WBC, CPK and K showed differences by the site of bleeding. Observed values for LDH and CPK varied with specimen type, plasma or serum; serum assay values showed greater variation than plasma values.