Artificial infestation of thinned plots of strains of upland cotton (PD 0786, LA HG 063, TAMCOT CD3H, MISCOT 7913-51, and DES 920) with neonate Heliothis virescens, (Lepidoptera: Noctuidae) between square initiation and 1 August in 1987 and 1988 at Mississippi State, MS resulted in 7-42% yield reduction relative to uninfested plots. Survival to day 2 was higher on TAMCOT than on the other strains. Yield loss per established larva was low for TAMCOT, moderate for LA HG, high for DES, and variable between years for RD and MISCOT. Total yield loss per plot followed the same pattern among strains as yield loss per established larva. Thus, TAMCOT was the most resistant strain tested (because of high tolerance) but was handicapped by having the lowest antibiosis. Loss of inner sympodial balls due to infestation resulted in gains in numbers of other bolls, but average boll weight was reduced up to 45% on infested plants. In this experimental system in which all strains were harvested simultaneously, early fruiting strains suffered lower yield losses.