An observational study was conducted to estimate prevalence and risk factors for carcass contamination by Salmonella and Campylobacter spp. in 60 lots of turkey slaughtered over 10 months in the province of Quebec, Canada. Carcass contamination was evaluated by the carcass rinse technique for about 30 birds per lot. Exposure to potential risk factors was evaluated with questionnaires, meteorological data, and cecal cultures. Multivariable binomial negative regression models were used for risk factor analysis. Prevalence of Salmonella-positive carcasses was 31.2% (95% confidence interval, 22.8 to 39.5%). Variables positively associated (P < or = 0.05) with the proportion of lot-positive carcasses were > or =0.5% of carcass condemnation due to various pathologies, cecal samples positive for Salmonella, low wind speed during transportation, closure of lateral curtains of truck during transportation, and slaughtering on a weekday other than Monday. When only Salmonella-positive cecal culture lots were considered, the proportion of carcasses positive for Salmonella was significantly higher in lots exposed to a >5 degrees C outside temperature variation during transportation, slaughtered on a weekday other than Monday, and in which > or = 4% of carcasses had visible contamination. Prevalence of Campylobacter-positive carcasses was 36.9% (95% confidence interval, 27.6 to 46.3%). The proportion of positive carcasses was significantly higher in lots with Campylobacter-positive cecal cultures and lots undergoing > or =2 h of transit to slaughterhouse. For lots with Campylobacter-positive cecal cultures, variables significantly associated with an increased incidence of carcass contamination were de4% of carcasses with visible contamination, crating for > or =8 h before slaughtering, and no antimicrobials used during rearing.