The concept of this book arose out of an international workshop, which we organized and held at the University of Wales Conference Centre at Gregynog. The workshop was the first occasion on which researchers from all the different disciplines concerned with the extracellular virulence factors of mucoid strains of Pseudomonas aeruginosa in relation to cystic fibrosis (CF) had met to discuss this multifaceted problem. It was deemed a particularly timely moment to gather together experts for the exchange of facts, ideas and hypotheses. No formal abstracts were presented and no proceedings were published. But during the succeed ing months the organizers were persuaded by a number of participants that a wider audience should benefit from what had proved to be such a fruitful cross-fertilization of expertise. Thus we moved from being workshop organizers to book editors, sure in the knowledge that at least we had a willing and enthusiastic set of contributors! It should be stressed, however, that this book is not a transcript of that workshop. Not all those participants are authors, and some new names have been added. Instead we have focused on alginate as an extracellular virulence factor of P. aeruginosa in CF pulmonary infections. Recent advances in the biochemistry and molecular genetics of alginate bio synthesis, as well as in our understanding of the basic defect in CF and isolation of the gene, mean that the book is even more timely than when first planned.