A study was conducted to estimate cost of major dairy cattle diseases. Forty (n=40) of the 167 dairy herds in Gyeongnam (Chinju) area were stratified and selected randomly for participation in the national animal health monitoring system. Gyeongsnag University veterinarians, Gyeongnam Livestock Promotion Institute veterinarians and clinic veterinarian visited each herd once a month for a total periods of 12 months. At a each visit data on disease, production, management, finance, treatments, preventive activities, animal events, and any other relevant events were collected. Monthly and annual cost estimates of disease treatment were in computed in each herd and stratum(including cost of prevention). Results were expressed as cost per head and given separately for cows, young stock, and calves. In cows, the most expensive seven diseases entities (from the most to the least) were : (1) clinical mastitis; (2) breeding problems; (3)gastrointestinal problems; (4) multiple system problem; (5) birth problems; (6) metabolic/nutritional disease; (7) lameness. In young stock, the most costly disease were the multiple system problems, breeding problems, respiratory disease, gastrointestinal disease, and lameness. In calves, the most costly disease problems were gastrointestinal problems, respiratory disease, integumental, multiple system problems, and metabolic/nutritional problems.