Biological measurements are undertaken to support a wide range of activities, from pharmaceutical development, forensic analysis and medical studies, to assessments of food safety and authenticity. Whatever the reasons for the measurements, it is essential that the data are reliable and fit for purpose. Method validation studies are essential for establishing the quality of measurement data. Validation is the formal process that provides objective evidence that methods of analysis are fit for purpose, and its importance is reflected by its inclusion in laboratory accreditation standards and other sectoral regulations and directives. This course offers an introduction to the key principles of validation for biological analysis and provides guidance on planning effective validation studies.