Avena spp. and Alopecurus myosuroides L. are noxious weed species of many cereal growing regions of Turkey. Aim of the study was to estimate economic thresholds of Avena spp. and A. myosuroides in terms of costs and returns at different wheat fields. The trials were conducted on four different wheat fields, which were selected to be representative for Samsun province in 2000-2001. After wheat emergence different weed densities were established. 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 non-linear regression model for both weed species. The determined economic thresholds of Avena spp. and A. myosuroides were based on the costs of herbicides registered against these weeds. Economic threshold for Avena spp. was between 11-20 plants/m(2) and for A. myosuroides between 23-39 plants/m(2).