The National Animal Health Monitoring System's Dairy 2002 surveyed dairy operations in 21 states representing 82.8% of U.S. dairy operations and 85.5% of U.S. dairy cows. One component of the study involved collection and culture of environmental samples for MAP from areas on the farm where manure from a majority of cows accumulated. Operations were selected based on perceived risk factors for Mycobacterium avium subspecies paratuberculosis (MAP) infection identified in an earlier questionnaire. Individual animal and environmental samples were collected and used to determine the efficiency of environmental sampling to determine herd infection status. Individual animal serum and fecal samples were used to classify herds as infected or not infected based on the presence of one test positive animal in the herd. Animals in lactation 2 and greater were selected for MAP testing. A total of 483 environmental samples were collected and 216 (44.7%) were culture positive for MAP. The highest percentage of positive environmental samples were collected from parlor exits (52.3%), floor of holding pens (49.1%), common alleyways (48.0%), lagoons (47.4%) and manure spreaders (42.3%). Of the 98 operations tested with environmental sample culture, 97 had individual serum ELISA and 60 had individual fecal culture. Of the 50 herds classified as infected by fecal culture, 38 (76.0%) were identified by environmental culture. Two of the 10 operations classified as not infected based on individual animal fecal culture were environmental culture positive. Of the 80 operations classified as infected based on serum ELISA positive test results, 61 (76.3%) were identified as environmental positive. Environmental sample culturing is more cost effective than individual animal sampling and identified more than 75% of infected operations.