Studies were conducted in Florida to evaluate interference of common cocklebur with peanut. Peanut yield reduction ranged from 0 to 88% for common cocklebur densities of 0–32 plants 8 m−1 of peanut row, and predicted loss was similar under normal moisture conditions. When moisture levels were above normal, the impact on yield was 9–24% less than when soil moisture was normal. Common cocklebur caused peanut yield loss if allowed to interfere for more than the first 2 wk after crop emergence, and peanut had to be common cocklebur free for at least 12 wk to prevent a yield reduction. These results show common cocklebur to be more competitive with peanut than other weeds evaluated previously.