Due to fast development of analytical methodologies, great importance is nowadays attached to the quality and reliability of the measurement data. This is influenced by a higher demand for regulatory compliance and under more exigent European and international standards such as the International Organization of Standardization/International Electrotechnical Commission 17025 norm for laboratory accreditation. This article focuses on method validation, traceability, measurement uncertainty (MU) of results, standardization, internal quality control (IQC), external quality control (EQC), and the role of method validation within quality assurance (QA).