The analytic precision of an automated blood analyzer, the Technicon H*1(R), was evaluated utilizing blood samples collected from 20 piglets at 1 and 14 days of age. The effect of storing the blood samples at 4 degrees C for 24 and 48 hours also was determined. Blood samples were analyzed twice on the first day and once on each of the subsequent tow days. Within-sample coefficient of variation was approximately 1% for hemoglobin concentration, erythrocyte count, hematocrit, mean cell volume, erythrocyte distribution width and hemoglobin distribution width (HDW); and approximately 5% for total leukocyte (WBC), neutrophils and lymphocyte counts. Mean HDW and automated differential WBC counts changed during storage to a degree that could be of clinical importance. Manual determination of differential WBC counts were compared with those obtained from the automated analyzer. Results correlated well for neutrophils (r=0.92 in 1-day-old and r=0.93 in 14-day-old piglets, P<0.001) and lymphocytes (r=0.85 in 1-day-old and r=0.93 in 14-day-old piglets, P<0.001). Other WBC values were too low to compare reasonably.