Studies were conducted over a 2-year period at Headland, Ala. and Jay, Fla. to evaluate the relationship between peanut seed size and tolerance of the resultant crop to normal and excessive rates of the herbicide paraquat (1,1′-dimethyl-4,4′-bipyridinium ion). Three seed sizes, termed small (3340 seeds/kg), medium (2615 seeds/kg), and large (1820 seeds/kg), were planted to achieve a common plant population. While seedling size at emergence reflected seed size, no interaction between seed size and herbicide treatment was detected for crop growth measured as the increase in canopy diameter over a 5-week period following herbicide application. None of the seed sizes resulted in seedlings that were either uniquely sensitive or abnormally tolerant of paraquat. Two sequential applications of paraquat at 0.14 kg ai/ha each was consistently the most damaging treatment as measured in growth reduction, however yield was reduced in only one of four trials. Seed size had an effect on yield in only two of the four trials, and within these two trials the average yield improvement from large seed relative to medium and small seed was only 10 and 12%, respectively. Net return generally was independent of seed size. However, medium-sized seed resulted in maximum net return in two out of the four experiments.