In the fall of 1983, 322 western calves, in five different groups, were bled on arrival at two Ontario feedlots. Calves receiving treatment for respiratory disease, within 35 days of arrival, were denoted as cases. The hematology and serum chemistry parameters of cases were compared to those of controls. Cases had significantly (p less than 0.05) lower hematocrits, fewer platelets, and more band cells on arrival, than did controls. Cases also had lower serum phosphorous, magnesium, potassium, iron and alkaline phosphatase levels, and increased bilirubin and aspartate aminotransferase levels relative to controls. Based on the results of multivariable logistic regression, hematocrit, platelet numbers, serum phosphorous, iron and aspartate aminotransferase levels were the most significant parameters for the prediction of respiratory disease. Reference values for stressed feedlot calves were created. Most parameters were distributed in an approximately normal manner, however the group to group variation in most parameters was significant.