This study was carried out to determine the influence of water deficit on yield and yield components of winter wheat under Thrace conditions. Four wheat genotypes (MV-17, Flamura 85, Saraybosna and Kate-A-1) were grown under five different water stress treatments during the 1998/1999 and t999/2000 growing seasons. The water stress treatments were unstressed control (S0), water stress at the late vegetative period (SO, at the flowering period (S2), at the grain formation period (S3) and the full stress (non-irrigation S4). The effects of water stress treatment on grain yield and yield components were statistically significant compared with non-stressed conditions. Grain yield under non-irrigated conditions was reduced approximately 40 %. Among the genotypes, MV -17 gave the highest grain yield.