Information concerning the interaction of reniform nematodes and silverleaf whiteflies on cotton is very limited, but could be of great concern to cotton growers and cottonseed producers in the Lower Rio Grande Valley (LRGV) of Texas. Studies were conducted to ascertain the singular and combined effects of the reniform nematode and silverleaf whitefly on lint yield, fiber quality, and seed quality. In the 1995-1996 yield and fiber quality field studies, reniform nematodes were observed to reduce lint yield by 29.5%, whereas silverleaf whiteflies caused yield losses of 21.9%. The greatest effect on fiber quality was a reduced micronaire in the whitefly-infested plots. Additional studies indicated that seed quality could be severely reduced by a high whitefly-infestation year. Reniform nematodes appeared to reduce seed quality to a lesser extent. Results show the significant yield losses that can be expected from these pests and the problems that could be encountered in both producing lint and seed under reniform nematode and whitefly pressure.