While application of composite insulators on lines and at substations is increasing steadily, a key concern is possible ageing that can impact long-term performance and service life. Many artificial and natural ageing tests and procedures have been proposed to help predict performance. In parallel, artificial pollution laboratory tests have been developed to assess hydrophobicity properties essential to good pollution performance. This presentation traces the historical development that influenced the standardization process in CIGRE and IEC. Results using different test methods and from test station experience are compared and systematic evaluation of data is applied to develop design tools to estimate ageing performance.