The performance of 24 F₁ hybrid populations of cotton, obtained by crossing each of 12 male sterile lines to 2 pollen-fertility restoring lines, was evaluated from tests conducted at two locations. Measurements for yield of seed cotton/plant, lint percent, number of bolls/plant, boll weight, weight of 100 seeds, earliness, length of fiber, fiber fineness, uniformity index and fiber strength were analyzed to obtain estimates of general and specific combining ability. The values of the general combining ability effects of lines were more pronounced than effects of specific combining ability. An evaluation of variance components revealed that the variance for general combining ability for the ten traits studied were all positive, while the specific combining ability variances were negative in five of the ten traits studied. Heterosis was detected for all traits; however, the magnitude of neterosis was usually smaller than that for yield, bolls/plant and boll weight. Heterosis for yield ranged from 20.90% to 52.27%. In most cases, heterosis for yield was associated with high heterosis for number of bolls/plant, boll weight and weight of 100 seeds.