Experiments were conducted under rain-fed conditions at Lethbridge, Alberta to determine the effect of short-term fall rye (Secale cereale L.), winter wheat (Triticum aestivum L.) and no cover crop treatments in the fallow year on weed growth. Under favorable weather conditions fall rye was as effective as post-harvest plus early spring tillage or herbicides in spring weed control. Winter wheat and fall rye residues, after growth was terminated in June, reduced weed biomass in September by 50% compared to no cover crop in 1993 but had little effect on weeds in 1995. A fall rye cover suppressed annual sow-thistle, flixweed, stinkweed, foxtail barley, Canada thistle and dandelion but not thyme-leaved spurge and downy brome. Wheat initially suppressed weed growth but did not have a long-term effect on as many weed species.