The design and analysis of experiments is typically taught as part of a second level course in statistics. Many different types and levels of students will require this information in order to progress with their studies and research. This text is thus offered as an introduction to this wide ranging and important subject. It has the advantage of explaining in an accessible way the basic principles behind good experimental thinking, planning and action. The authors have used their experience in teaching related courses to separate out what seem to be the essential basic contents for everyone, and to combine with these some of the most useful additional topics in biological, industrial, medical, and environmental experimentation.