Despite increasing awareness of the importance of passive immunity in calves to reduce disease prevalence, morbidity from calfhood diseases, days to first illness, sick days, days of viral shedding, viremia, growth and productivity(l-6), 20 to 30% of neonates will be hypo- or agammaglobulinemic. Failure of passive transfer of maternal immunoglobulins (FPT) occurs when there is a problem with 1 or more of the 3 phases of passive transfer: formation of colostrum with a high concentration of immunoglobulin, ingestion of an adequate volume of colostrum by the calf in a timely fashion, or efficient absorption of colostral immunoglobulin. Some calves with FPT are healthy and productive neonates, which is a reflection of the importance of other factors including environmental conditions, management practices, pathogen load, pathogen virulence, and nutrition of the calf in addition to acquisition of passive immunity. There is general acceptance that failure of passive transfer exists when calves between 36 and 48 hours of age have serum immunoglobulin concentrations less than 1000 mg/di. Individual calf problems can occur when its serum immunoglobulin concentration is below 1000 mg/di; herd problems occur with increased prevalence of scours and respiratory disease occur when large numbers of calves have FPT.