Australian research into the economics of privately and publicly funded weed control is reviewed. Of the published studies that consider farm-level problems, most have been simplistic. Complexities which affect a farmer's optimal control strategies for crop and pasture weeds are outlined. The determination of herbicide rates on an economic basis is proposed as an area for further work. The traditional economic threshold concept is not suitable for this purpose. Studies of the economics of public weed control programs are slightly more common than farm-level studies in the literature, although work on public weed problems has focussed on just a few weed species. Future directions for weed economics research are suggested.