Johne 5 disease, or paratuberculosis, is a chronic, infectious, wasting disease that affects dairy cattle. Estimation of its economic impact on U.S. diary operations was part of the USD A National Animal Health Monitoring System’s (NAHMS) 1996 national dairy study. Herds that tested positive for the disease and reported cull cows showing clinical signs experienced reduced milk production of over 450 kg per cow, culled more cows but had lower cull cow revenues, and had greater mortality than herds that tested negative and showed no clinical signs of Johne’s disease. These production impacts resulted in test positive clinically positive herds experiencing an economic loss of $157-$166per cow inventory. Nationally, these losses translate to a $36-$38 per cow cost which is at least a third more than previous estimates.