The transfer of colostral IgM and IgG to newborn calves was studied quantitatively. Both IgM and IgG were absorbed equally well from the gastrointestinal tract of the calf. However, the degree of globulin absorption and hence the serum immunoglobulin concentrations varied considerably from calf to calf. Three of the ten calves remained virtually agammaglobulinaemic despite the ingestion of colostrum. The significance of failure to absorb colostral immunoglobulins (especially IgM) is discussed in relation to the pathogenesis of neonatal septicaemias of the newborn calf.