\'Martin\'s axiom\' is one of the most fruitful axioms which have been devised to show that certain properties are insoluble in standard set theory. It has important 1applications m set theory, infinitary combinatorics, general topology, measure theory, functional analysis and group theory. In this book Dr Fremlin has sought to collect together as many of these applications as possible into one rational scheme, with proofs of the principal results. His aim is to show how straightforward and beautiful arguments can be used to derive a great many consistency results from the consistency of Martin\'s axiom.