Yellow nutsedge (Cyperus esculentus L.) was hoed in two cotton (Gossypium hirsutum L. 'Acala Si-21) fields each year (1979 to 1981) for 2 to 12 weeks after crop emergence to evaluate the influence of several weedfree periods on the growth and reproduction of nutsedge and yields of cotton. Compared to the control (plots receiving only cultivation), a 2 week weed-free period reduced the average number of nutsedge shoots at harvest by 52% (61 vs. 29 shoots/m²). Additional hoeings for 4 to 12 weeks further reduced populations by 67 to 87%. Compared to tubers counted in the spring, populations of tubers in control plots increased 3 to 12-fold by harvest. However, compared to control plots, 2 weekly hoeings reduced tuber populations at harvest by 70 to 90% (895 vs. 221 tubers/m² and additional hoeings tended to reduce or reduced tuber populations further (75 to 98% reduction). When cotton yields were reduced in control plots in 1979 and 1980, a 2 to 6 week weed-free period substantially reduced yield losses. Averaged over six locations, yields in plots with a 4 to 12 week weed-free period were greater than yields of control plots.