The economic impact of weeds on farms in the New England Region of New South Wales is estimated from data from a cross -sectional survey. Weeds can be classed as noxious or declared plants, plants that the farmers perceived as weeds, and trees -- which many farmers also perceived as weeds. Variables were defined for several levels of intensity of infestation for each of these three classes of weeds. The impact of each these variables, on property income and stocking, was estimated through Cobb-Douglas production functions. The presence of very-heavy infestations of non-noxious weeds, and heavy infestations of non-noxious weeds, were found to be associated with reductions in income. In total, the income of the representative property would be increased by 15 per cent, ceteris paribus, if these infestations were removed.