Agricultural machinery is a major source of injury on farms. The importance of machinery safety practices as potential determinants of injury remains incompletely understood. We examined two such safety practices as risk factors for injury: (1) the presence of safety devices on machinery and (2) low levels of routine machinery maintenance. Our data source was the Saskatchewan Farm Injury Cohort baseline survey (n=2390 farms). Factor analysis was used to create measures of the two operational safety practices. The farm was the unit for all analyses and associations were evaluated using multiple Poisson regression models. Limited presence of safety devices on machinery during farm operations was associated with higher risks for injury (RR 1.94; 95% CI 1.13-3.33; p(trend)=0.02). Lower routine maintenance scores were associated with significantly reduced risks for injury (RR 0.54; 95% CI 0.29-0.98; p(trend)=0.05). The first finding implies that injury prevention programs require continued focus on the use of safety devices on machinery. The second finding could indicate that maintenance itself is a risk factor or that more modern equipment that requires less maintenance places the operator at lower risk. These findings provide etiological data that confirms the practical importance of operational safety practices as components of injury control strategies on farms.