The CSIRO Cotton Cultivar Trial(CCT) has been run cooperatively by CSIRO and DPIQ for 24 years and is used as the last stage in our breeding line evaluation. Early generation testing following single plant selection involves unreplicated progeny rows at the Australian Cotton Research Institute, further progeny row tests and multiple row replicated trials at a limited number of farm sites. At each stage, lines with poor seedling vigour, disease susceptibility poor fibre quality or low yield are removed from further testing. The CCT involves 13 irrigated sites and three dryland sites in all major cotton growing regions in Australia. Management is normal commercial practice including full insect control. Entries in the CCT include promising breeding lines and commercial standards. Plots consist of three or four rows from 10 to 14 metres long. There were five replications in the 1996/97 trials and four in 1997/98. The centre rows of all plots are harvested with a modified picker, the seed cotton weighed and a subsample is taken for ginning at Biloela or Narrabri and fibre quality analysis at Narrabri. The most promising lines are retained in the scheme and also seed increased. In this way, by the time good performance is confined, sufficient seed is available for large scale testing and final seed increase for commercial use.