Based on the timing and location of 400 successful releases of insects specifically targeting Echium species of weeds including PatersonÕs curse / ÒSalvation JaneÓ since 1992 across southern Australia, and estimates of insect attack and spread rates according to dates of weed germination, a benefit / cost analysis is developed for the biological control research and development program begun by CSIRO in 1972. Australian meat and wool industries have also contributed funding to the program, in addition to in-kind contributions of the NSW, Victorian, South Australian and Western Australian state departments, and since 1995 the Weeds CRC. Total R&D expenditures by CSIRO and the partners mentioned above will reach $14 million by 2001. Annual benefits in terms of increased productivity of grazing lands are projected to rise from near-zero in 2000 to some $73 million by 2015, based on a value of $8/DSE. These sums do not include savings due to reduced spray costs as offsetting expenses will arise with management practices required to maximise the success of bio-control agents, and to limit reinvasion by other pasture weeds. The discounted (5%) net present value (NPV) of the benefit-cost stream from 1972 to 2015 is projected at $259 million, for a B/C ratio of 14:1 and an internal rate of return exceeding 17%. Because lower attack and spread rates of the insects are observed in regions with late autumn breaks, a slow build-up of benefits is expected to continue over many years. The discounted NPV for the 1972-2050 period is estimated to be $916 million, with a B/C ratio of 47:1 and an internal rate of return exceeding 19%.