Technical Abstract: The reniform nematode (Rotylenchulus reniformis) is a major, yield limiting pest to cotton (Gossypium hirsutum) production in the Lower Rio Grande Valley of Texas, as well as to cotton production along the Red River and Mississippi Delta, and in the Southeast. Four germplasm lines, C221-91, C224-91, C300-01, and C306-91 were developed and released cooperatively by the USDA-ARS, Texas Agricultural Experiment Station, and Rio Farms, Inc., because of their good adaptability to the Lower Rio Grande Valley, the Coastal Bend area of Texas, and the southern region of Tamaulipas, Mexico. In addition, C224-91, C300-91, and C306-91 have shown good tolerance to the reniform nematode and C224-91 appears to have field tolerance to the southern root-knot nematode (Meloidogyne incognita). In tests conducted from 1992-1994, in fumigated and reniform nematode- infested plots, C224-91, C300-91, and C306-91 had yield reductions that were less than 50% of the reduction observed for Stoneville 453. Fiber quality of the four lines was usually equal to or better than Deltapine 50, with lint percent being 1.5 to 2.0% greater.