The blastogenic response of peripheral blood mononuclear cells to mitogenic stimulation by concanavalin A was lower (P less than 0.01) after transporting 60 dairy calves 480 km than it was either one or two weeks later. The response was similar for phytohemagglutinin. There was a decrease (P less than 0.05) in the number of peripheral blood monocytes and neutrophils two weeks after shipping. The transportation of calves did not affect plasma IgG1 or IgM level. The mitogenic stimulation of peripheral blood leukocytes by both phytohemagglutinin and concanavalin A in whole blood cultures was more variable than with the culture of peripheral blood mononuclear cells. Technique variation, which was defined as the coefficient of variation among quadruplicate cultures, was greater than 20% for while blood assays and less than 10% for cultures of peripheral blood mononuclear cells. The variation among different calves tested at the same time and the variation within single calves tested at different times were also lower in peripheral blood mononuclear cell cultures than in whole blood mononuclear cell cultures than in whole blood assays. It is suggested that the variation among replicate cultures be reported in blastogenesis studies.