The RIM (resistance and integrated management) model is presented. RIM represents a wide diversity of herbicide and non-herbicide options for management of Australia's most important crop weed, Lolium rigidum, in the context of the non-irrigated extensive farming system of southern Australia. Enterprise choices in the model include cereals, lupins, canola and three types of pastures for grazing by sheep. Users of RIM may specify the enterprise sequence and any feasible combination of the 35 weed treatment options each year over 10 or 20 years. Weed treatment options include selective herbicides (11), non-selective herbicides (5), non-chemical treatments (16) and user-defined treatments (3). The model represents weed and seed bank population dynamics, weed-crop competition, weed treatment impacts (including phytotoxicity), agronomic details, and financial details. Economic and biological model results are presented for scenarios with differing levels of availability of selective herbicides and different rotational sequences. (C) 2003 Elsevier Ltd. All rights reserved.