This study was carried out at Sakha Agricultural Experimental Farm to study the effect of crop rotation on weeds and inturn on wheat grain yield. The trial were initiated in 1992/93 winter season and com­pleted in 1994/95 winter season where no weed control treatments were applied at the last season. Data indicate that canary grass (Phalaris spp.) dominated all weeds in the experimental area. The results of 2-year crop rotation ensure the benefits of berseem as a preceding winter crop to wheat where this crop greatly reduced number and fresh weight of canary grass assessed in wheat preceded by berseem. The grain yield produced from this sequence was significantly highercompared with that produced from faba bean/wheat and wheat/wheat sequence. The poor­est weed control and the lowest wheat grain yield was recorded for the crop sequence wheat/wheat. The 3-year crop rotation indicate that the lowest number and fresh weight of Phalaris spp. were recorded for the treatments of the crop sequenceberseem/berseem/wheat. There was no significant differ­ence among all treatments in this sequence and yielded the highest wheat grain yield. The poorest weed control and the lowest wheat grain yield was found for the crop sequence wheat/wheat/wheat.