In vitro neutrophil function was assessed in two English Springer Spaniel dogs, two Bichon Frise dogs, and one Chow Chow dog with congenital ciliary dyskinesia; three clinically normal English Springer Spaniel dogs that were presumed heterozygous for congenital ciliary dyskinesia; and five control dogs. Chemotaxis and random migration in affected and heterozygous dogs were found to be comparable to those of control dogs. Increased (P less than or equal to 0.05) neutrophil adhesion, antibody dependent cell-mediated cytotoxicity, iodination of proteins, and oxygen radical production in neutrophils from affected dogs were probably the result of chronic bacterial infection in vivo. Bacterial ingestion by neutrophils from the three heterozygous English Springer Spaniel dogs was significantly increased compared to control dogs but was not different from affected English Springer Spaniel dogs, suggesting a breed-related phenomenon. Significant decreases in neutrophil function were not seen in any of the dogs with congenital ciliary dyskinesia, indicating that a defective microtubular system is not shared by respiratory cilia and neutrophils and that defective neutrophil function does not contribute to respiratory infection.