The experiment with crop rotation and monoculture of winter wheat was conducted at the Agricultural Experimental Uhrusk. It was set in the method of split-plots which was designed with four repetition. The grey-brown rendzina soil was formed from light loam weak sandy. The subject of the experiment were the number, air dry matter and species composition of weeds in the crop rotation and monoculture of winter wheat. This cereal was weeded mechanically or chemically (with herbicides). It was affirmed that a greater number of weeds and air dry matter of weeds were in the monoculture than in crop rotation. The following weeds were in crop rotation with winter wheat: Chenopodium album, Fallopia convolvulus, Galium aparine, Meland rium album, Viola arvensis and Polygonum aviculare, but in the monoculture: Consolida regalis, Stellaria media, Amaranthus retroflexus, Chenopodium album, Galium aparine and Fallopia convolvulus.