Five female Holstein-Friesian calves were clinically suspected of suffering from Bovine Leukocyte Adhesion Deficiency (BLAD), because of multiple recurrent infections and persistent leucocytosis. The diagnosis was established by a Polymerase Chain Reaction (PCR) technique, by which a point mutation in the DNA encoding for the CD18 allele was detected. The animals either died spontaneously or were killed because of incurable life threatening infections. Gross post-mortem examination revealed severe and extensive necrotizing processes mainly located in the respiratory and digestive tract. Microscopic examination of these necrotizing lesions demonstrated a lack of extravascularly located polymorphonuclear granulocytes (PMN) although vascular leucocytosis was obvious. However, extensive catarrhal bronchopneumonia was noticed with marked infiltration of the alveoli and bronchioli by PMN. These findings are discussed in relation to the pathogenesis of BLAD.