Comparative efficacies of fipronil and azinphosmethyl were assessed against high population levels of boll weevils in small plot (12 rows by 100 ft) tests. When insecticides were applied at 7-d intervals, beat net samples indicated that fipronil temporarily reduced boll weevil population levels, but efficacy was not sufficient to prevent population increases between applications. Whole plant samples indicated that populations were not reduced by either insecticide. A lower percentage of squares were oviposition punctured in the fipronil treatment than in other treatments, but numbers of oviposition punctured squares per plant were similar among treatments. When insecticides were applied at 3-d intervals, both fipronil and azinphosmethyl reduced boll weevil numbers in beat net and whole plant samples, and both materials reduced the percentage of oviposition punctured squares. However, the number of punctured squares per plant was highest in the fipronil treatment. Leaf bioassays indicated that both fipronil and azinphosmethyl were highly effective against boll weevils immediately after application, but residual activity of fipronil was greater than that of azinphosmethyl. Boll weevil population trends in the untreated check tended to follow a pattern similar to those of the insecticide treatments, indicating that the plot size used was too small to prevent considerable inter-plot movement of adult weevils.