Avena spp. and Alopecurus myosuroides are noxious weeds in many cereal-growing regions of Turkey. The aim of the study was to estimate economic thresholds of wild oat and black grass in terms of costs and returns in different wheat fields. The trials were conducted in 2000-2002 in two different wheat fields, which were selected to be a representative for Samsun province. hi these fields, the plots each 2 m in size had different weed densities of 1, 5, 10, 20 and 40 plant m(2) maintained after wheat emergence. In addition, weed-free control plots were set up in the same fields. After harvest, the effect of different densities was calculated as % yield losses compared to control plots. The % yield losses were correlated to the weed density using a linear regression model for both weed species. The economic thresholds of wild oat and black grass were determined in terms of the herbicides registered against them. Economic threshold for wild oat was between 11.77-14.70 plants/m(2) and for black grass 15.70-32.56 plants/m(2).