In Australian grain-growing regions, the evolution of weeds resistant to multiple herbicides threatens the sustainability of existing cropping systems. As a result, herbicide susceptibility is considered to be a potentially exhaustible resource. Based on a survey of 132 Western Australian grain growers, perceptions of various factors relating to the herbicide resource were measured. These include the rate of resistance evolution, cost of resistance, the future availability of replacement herbicides, reductions in the level of resistance in a population over time, and mobility of resistance. Growers were found to have a generally high level of awareness of herbicide resistance and consider it to have a high potential cost. However, many perceive that the stock of effective herbicides is likely to be renewed in the short term, either through new herbicide development or resistance reversion. Potential opportunities for targeted extension to improve farmer decision-making are identified. (C) 2002 Elsevier Science Ltd. All rights reserved.