This thesis records my involvement in bacterial cell surface research which began in 1971 during my PhD programme with early studies on the biosynthesis and chemistry of klebsiellapolysaccharides. A detailed study of the chemistry of the pneumococcal teichoic acid followed and here I was introduced to immunochemistry. The structure and immunochemistry of the surfaces of anaerobic bacteria, particularly of the Bacteroides species and the clostridia, then become a major interest. Clostridium difficile played an important part in this section, where the most significant contribution showed conclusively that it was an infectious agent. Links with the Moredun Research Institute have resulted in collaborative studies on the important veterinary pathogens Pasteurella haemolytica and P. multocida, and a study of the bacteriology of periodontal disease in sheep. Concurrent with this have been other collaborative studies on bacterial surfaces, in particular the group B streptococci. The major current interest is on the chemistry and immunochemistry of bacterial lipopolysaccharide (LPS) with a particular interest in its interaction with antibodies (leading ultimately to immunotherapy of septic shock and Gram-negative sepsis) and the environmental influence on LPS expression by bacteria and its subsequent detection.