Fipronil was evaluated for boll weevil control in cotton at the Yaqui valley of Sonora, Mexico. 25, 50 and 100 g ai/ha of fipronil were compared to the commercial standard azinphos methyl 500 g ai/ha. Results indicated no significant differences in mortality 48 hours after application on 3 to 5 day old adults of the boll weevil. Residuality test showed that reinfestation 2 days after spraying and mortality recorded 2 days later did not present significant difference between fipronil 50 g ai/ha and azinphos methyl 500 g ai/ha. However, reinfestation 7 days after application and mortality readings 2 days later, indicated that fipronil was significantly different from azinphos methyl with 16.1 % and 5.0 % mortality respectively. Even though there was a significant difference from the statistical analysis, from the biological point of view this mortality is not considered important. Fipronil represents a new alternative for insect management strategies established in the Yaqui valley.