A 3-year study was conducted to determine if testing mosquitoes collected in modified sentinel chicken boxes for West Nile virus (WNV) or testing sentinel chickens for WNV antibody would detect WNV activity before onset of human cases in East Baton Rouge Parish, LA. In each year mosquitoes tested positive for WNV before the onset of human cases were detected, but seroconversions of sentinel chickens were detected after the human cases occurred. In 1 year we also compared the effectiveness of Centers for Disease Control and Prevention (CDC) light traps, gravid traps, and sentinel chicken box traps for collecting WNV-positive mosquitoes. Gravid traps collected more WNV-positive mosquitoes than CDC light traps or sentinel chicken box traps. However, WNV was detected earlier in mosquitoes collected from sentinel chicken box traps than in mosquitoes collected with gravid traps or CDC light traps. In total, 1,222 pools containing 19,353 mosquito specimens representing 18 species were tested for WNV. West Nile virus was detected in 59 mosquito pools from 4 species; 87% of the positive pools were detected from Culex quinquefasciatus, which was the most abundant species collected in all 3 years.