Peripartum immune response, disease occurrence, and production were evaluated in 136 Holstein cows and heifers from three herds. Based on antibody to ovalbumin (OVA), animals were classified using a mathematical index into high (Group 1), average (Group 2) or low (Group 3) antibody groups. Whey antibody to OVA and serum antibody to Escherichia coli similarly reflected the ranking of groups for serum antibody to OVA. Unstimulated and OVA-stimulated lymphocyte proliferative responses were inversely related to antibody group. Group 1 animals had the highest lymphocyte proliferative responses to concanavalin A peripartum, the greatest decrease in response at calving, and the greatest increase in response postpartum. Delayed type hypersensitivity to tuberculin did not significantly associate with antibody group. Group 3 animals had a higher projected 305-day yield for milk, fat, and protein than Groups 1 and 2; however, in two of the three herds evaluated, Group 1 animals had no clinical mastitis.