This study was conducted to evaluate the effects of selected morphological traits in near-isogenic lines of cotton (Gossypium hirsutum L.) on lint yield, lint percent, and fiber quality under natural insect infestations. Five morphological traits (i.e., okra leaf, nectariless, frego bract, smooth leaf, and glandless) were compared to the normal checks in eight genetic backgrounds (i.e., 'Deltapine 16', 'Stoneville 2131', 'Auburn 56', 'Delcot 277', 'Coker 310', 'Coker 201', 'TH 149', and Pee Dee 2165). Replicated experiments were conducted under irrigation and without insecticide applications at two locations in Oklahoma for 3 years. In the analyses combined over years within each location, the interactions of morphological traits X genetic backgrounds were significant at both locations for lint yield, were inconsistent between locations for picked lint percent and fiber length, and were not significant at either location for fiber length uniformity, fineness, or strength. The nectariless lines were comparable to the checks for lint yield and lint percent. The okra-leaf lines were also comparable to the checks for lint yield, but were frequently lower for lint percent. The large and consistently significant reductions in lint yield and lint percent of the frego-bract lines were at least partly due to their greater susceptibility to the cotton fleahopper [Pseudatomoscelis seriatus (Reuter)]. The smooth-leaf lines, despite their suppression of fleahopper infestations and bollworm [Heliothis zea (Boddie)] oviposition, often displayed lower lint yield that the checks, possibly resulting from lower lint percent (a component of lint yield). The lint yield and lint percent of the glandless lines were reduced in some genetic backgrounds. Differences in fiber length were few and inconsistent in direction. No significant differences were found in fiber length uniformity, fineness, or strength at either location. Based on these results (as well as the insect responses), the frego-bract trait should not be incorporated in the Oklahoma cotton breeding program; the smooth-leaf and glandless traits appear unpromising and probably should not be used; and the nectariless and okra-leaf traits should likely receive some attention.