An assessment of Johne's disease on US dairy operations was part of the National Animal Health Monitoring System (NAHMS) Dairy '96 Study conducted during 1996. Data and biologic samples were collected from randomly-selected dairy producers in 20 states, representing 83% of the national dairy cow population. From February through May of 1996, each respondent dairy producer was visited by a federal or state animal health official and completed a questionnaire assessing producer awareness of Johne's disease and use of management practices reportedly linked to Johne's disease. Blood samples were collected from milk cows on the operations during the visit and sent to the National Veterinary Services Laboratories for M. paratuberculosis testing using the IDEXX ELISA. National and regional US seroprevalence of M. paratuberculosis at the herd-level will be estimated. In addition, producer familiarity with and recognition of Johne's disease on the operation will be assessed. The frequency of use of certain management practices reportedly linked to the spread of this disease will be assessed. These include: maternity management (calving location, bedding management, use of calving area by sick cows), neonatal heifer management (time of calf separation from dam, washing of teats before colostrum removed), heifer management (physical contact and sharing of feed or water with adult cattle, use of manure handling equipment for heifer feeds, use of Johne's vaccine), and introduction of cattle to the operation.