This paper presents a new model which incorporates features of developing country agriculture that may be critical in shaping the welfare outcomes of alternative agricultural policies. The model features heterogeneous households linked through markets in a rural economy-wide structure, with endogenous market participation for farmers facing transactions costs. The model is used for policy simulations, including market price support, production subsidies, input subsidies, transaction cost removal, and unconditional cash transfers. Applications for six countries highlight the diversity of potential impacts of such policies. The simulation results suggest that there are circumstances under which some market interventions, such as input subsidies, may be only slightly less efficient at transferring incomes than direct payments.