Australian research and development organizations invest substantial grower and/ or taxpayer (public) funds, on the control of weeds in broad-acre cropping using herbicide. Benefits from this research are distributed between growers, consumers and the agrichemical industry depending on the patent status of the technology adopted or discarded due to the research. The size and allocation of the benefits from “public” R&D affecting on-patent and off-patent herbicide use is analysed using economic surplus techniques. The results indicate that herbicide patent status does not have important implications for “public” R&D investment decisions.