Sera from hogs were analyzed using the modified direct agglutination test (MAT). Serum samples were collected from sows which were part of the National Animal Health Monitoring System (NAHMS) swine survey. The blood sera on file represented 394 randomly selected hog farms throughout the United States. Additionally, the NAHMS survey included information on type of production facilities and level of cat, dog, or bird access to the facilities. Of the sows tested 19 percent tested positive for toxoplasmosis. This study showed a positive relationship between sows or herds testing positive for Toxoplasma gondii and three factors: 1) method of rodent control, 2) type of production facility, and 3) access of certain animals (cats, dogs, birds) to production facilities. These data indicate that it will be difficult to eliminate T. gondii from swine herds which allow cat or dog access to facilities. Use of cats as a method of rodent control should be discouraged. We found a strong association between use of "bait only" for rodent control and the herd testing negative as compared to the use of "cats only" for rodent control. Greater industry awareness is needed for methods of rodent control through the use of baits. Sows in herds where female replacements were raised internally were significantly more likely to test positive for toxoplasmosis. Sows in confinement facilities had a significantly lower prevalence of Toxoplasma gondii. Herds testing positive were significantly smaller than those which were negative. In general, there were not any regional differences in prevalence rates. Sows testing positive did not have a reduced level of productivity.