Duration and density experiments were conducted in the field to measure horsenettle (Solanum carolinense L. # SOLCA) interference with Spanish and runner-type peanuts (Arachis hypogaea L. ‘Pronto’ and ‘Florunner′). Spanish peanut yield generally was higher with 6 to 8 weeks of weed-free maintenance. Horsenettle interference for 6 to 8 weeks did not decrease the yield of Spanish peanuts, and interference for 6 weeks did not decrease yields of runner peanuts. Weed-free maintenance for 2 or more weeks allowed increased runner peanut yield when compared to weedy plots. Linear regression predicted a 69 kg/ha Spanish peanut yield increase for each week of weed-free maintenance. Linear regression predicted a Spanish peanut yield reduction of 40 kg/ha for each week of weed interference in 1983, the only year in which the slopes of the regressions were statistically significant Curvilinear equations with the runner-type cultivar predicted an 81 kg/ha yield increase or 96 kg/ha decrease for each week of weed-free maintenance or weed interference, respectively. In 1 of 2 yr, Spanish peanut yield was reduced by horsenettle at a density of 32 plants/10 m of row.