Originally written for those wishing to design or conduct epidemiological studies and as a graduate course text, and published to wide international acclaim, this book now appears in paperback. Its coverage of all relevant issues will thus be accessible to all students of epidemiology. Much epidemological research is undertaken to relate exposure to external agents to the occurrence of particular diseases, which depends critically on the accurate measurement of exposure. This book is the first to cover the design of questionnaires, conducting personal interviews, abstracting medical records, the use of biological and environmental measurements, and important background areas for exposure measurement, such as error in measurement and its effects, maximising participation of subjects in research, and ethical issues.