Swine dysentery was eradicated from a 270 sow herd by using medication in conjunction with cleaning and disinfection, without reducing the herd size. The feed conversion efficiency, cost per kg liveweight gain and veterinary costs in the herd were compared with similar Meat and Livestock Commission recorded herds before swine dysentery entered the farm, while it was present and after its eradication. During the four years when the disease was endemic in the herd the feed conversion efficiency deteriorated by 0.58, equivalent to 7.31 pounds per pig, the cost per kg liveweight gain was 15 per cent higher and the costs of veterinary care and medicines were 1.38 pounds per pig greater. Although there were pigs with clinical swine dysentery in the herd during the four year period, the poor production figures were attributed mainly to subclinical disease. The cost of eradicating the disease was more than 20,000 pounds but this sum was recouped within 12 months by the improved production and reduced drug usage. The chances of success of such a programme have been estimated to be between 54 and 90 per cent.