The performance of CSIRO varieties and new lines are evaluated each year in a series of regional trials, known as the Australian Cotton Cultivar Trial (ACCT). CSIRO and the QDPI have been running these trials since the 1974/75 season. Currently the ACCT comprises thirteen sites representing all the major cotton growing areas. This wide testing provides a good estimate of overall performance while also enabling assessment of whether particular genotypes perform relatively better at some environments than others.