This third edition has been completely rewritten. It aims to teach the fundamentals of heterocyclic reactivity and synthesis in a way that is understandable to undergraduate students. More advanced material has also been added, making it appropriate both for postgraduate courses and for those involved in heterocyclic chemistry in industry. Early chapters present essential teaching material in concise resumes suitable either as introductions or as summaries for revision. Added exercises and solutions should help students understand and apply principles. The text then discusses the chemical reactivity and synthesis of particular heterocyclic systems. Original references are included throughout, as well as many review references.