Bacterial pathogenesis is heavily dependent on the capacities of microbial cells to avoid activating or to resist antimicrobial mediators of neutrophil polymorphonuclear granulocytes, the first line of phagocytic defense against infection. These capacities can but be understood in terms of the cell biology of neutrophils. The relevant microbial mechanism largely reside in the biochemical structures of their cell surfaces and their secretions. These factors are reviewed, and the importance of biochemical genetic analysis in seeking new solutions to old and new problems is stressed.