Cotton breeding lines and cultivars were planted in two blocks in Houston clay Soil. One block was infested with two-spotted spider mites at the 6th leaf stage. Spider mite damage was assessed on 2 dates by rating the amount of apparent damage and assigning a Damage Index value. Plants were sampled at first bloom and the amount of condensed tannin analyzed. Yield was determined for each treatment and fiber analysis obtained to compare the effects of spider mites on cotton. Yield reduction was the main effect of spider mite infestation. Fiber strength was the only fiber property effected but only on plant lines with high strength and which sustained great spider mite damage. The damage index value related to yield loss while the B 1/1 value for condensed tannin did not. This indicates that condensed tannin was not the only factor contributing to spider mite resistance.