Technical Abstract: Reniform nematodes (Rotylenchulus reniformis) can be a serious yield-reducing pest in many cotton (Gossypium hirsutum) producing areas of the Lower Rio Grande Valley of Texas, with typical symptoms being stunted and unhealthy appearing plants. Likewise, feeding damage by the silverleaf whitefly (Bemisia argentifolii) can result in severe plant stress, reduced yields, and lint contamination with honeydew associated fungi. In 1995, the effects of the reniform nematode and silverleaf whitefly on cotton was evaluated at the USDA North Farm, Weslaco, Texas. The results indicated the potential yield losses that the reniform nematode and silverleaf whitefly can cause. On the average, reniform nematodes reduced total yield by 45%; whereas, whitefly infestations appeared to reduce yield by 39%. The greatest yield reductions were realized in the second harvest, indicating that these pests may severely reduce the yield potential of the plant as the season progresses, especially if the pests attack the plant simultaneously. The deleterious late season effects that the reniform nematode and silverleaf whitefly appear to cause demonstrate the importance of managing for an early crop, as well as the need to use cultural practices that reduce or avoid these pests.