Reniform nematodes, which infest the soils of the Lower Rio Grande Valley of Texas, can cause severe reductions in yields of upland cotton. Symptoms of cotton plants infested by reniform (RN) nematodes are an unhealthy and stunted appearance and reduced fruit production and retention. In 1993, a field study was conducted in RN-infested and TELONE II-fumigated plots to determine the effects of the RN nematode on cotton cultivars and breeding lines and to ascertain if yield differences exist among the tested cotton germplasm grown in the fumigated and RN-infested plots. Cotton grown in the RN-infested plots showed a 29.3% reduction in total lint yield. In addition, when lint yields were compared across the fumigated and RN-infested plots, C21S781-2, a newly released germplasm line, produced the greatest lint yield, while CD3PIHP45H, a MAR strain showed no yield reduction due to RN nematodes. Fiber strength, length, uniformity index, elongation, and micronaire were not affected by the nematodes. Results indicate that some breeding lines may posses tolerance to RN nematodes.