Reniform nematode (Rotylenchus reniformis), infecting most cotton growing areas in the southeast including Alabama, can reduce cotton yield by up to 75%. This study was conducted to evaluate cover crops as biofumigants in controlling reniform nematodes in cotton under conservation tillage system. Two mustard cultivars [Pacific Gold (Brassica juncea L.) and Ida Gold (Sinapis alba L.)] and winter rye (Secale cereale, cultivar Maton) were used as cover crops in this study. Cotton (Gossypium hirsutum plant stand and rate of growth were compared among plots without (control plots) and with cover crops. Our preliminary data showed that all cover crops used in the test significantly reduced reniform nematode populations (range <500 to 2,000/150cc soil) from the initial nematode level of >3000/150cc of soil sampled in early spring. Moreover, both mustard cultivars produced significant biomass before the first frost in 2003. The following spring, however, Pacific Gold and winter rye grew vigorously and produced large biomass but Ida Gold minimally recovered from winter frost. Additionally, plots planted to Ida Gold yielded lower nematode counts and sustained better cotton stand compared to Pacific Gold and winter rye. Based on these results, Ida Gold is a promising cover crop for controlling reniform nematodes in cotton.