The dynamic nature of weed management often leads to shifting demands for research, development and extension specific to particular weeds and local farming systems. This study’s purpose was to inform decisions on how to best meet these demands by identifying the costs and management faced by growers across Australian grain growing regions, crops and weed types. This study provides the most comprehensive national analysis of the cost of weeds to Australian grain growers. It includes the cost of yield loss due to in-crop and fallow weeds, weed control costs including herbicide, non-herbicide practices and grain contamination costs. The study covered the 13 major agro-ecological zones across the Western, Southern and Northern grain growing regions and the major crop types of wheat, barley, oats, canola, pulses and grain sorghum. It examined the rate of uptake of established and emerging weed management practices, together with associated analysis of changes in crop seeding systems. The study was completed for Grain Research and Development Corporation (GRDC) by Dr Rick Llewellyn CSIRO, David Ronning and Michael Clarke AgEconPlus, Allan Mayfield of Allan Mayfield Consulting, Dr Steve Walker Uniquest, University of Queensland and Jackie Ouzman CSIRO.