In the Danish Salmonella Surveillance and Control Programme all swineherds are each month assigned to one of three salmonella levels. In order to clarify why an increasing number of chronic infected level 3 herds were unable to solve their salmonella-problems an advisory task force consisting of 5 veterinarians and 5 swine consultants was established. The task force worked out mandatory herd specific intervention plans in 78 swineherds. Twelve months after the implementation of the intervention plan, 61 herds (78%) was assigned to level I, 12 herds (15%) to level 2 and 5 herds ( 6%) to level 3. Of the 61 level I herds, 45 herds had been assigned to level I for six months in a row. This specific initiative shows that it is possible to reduce the number of chronic infected level 3 herds by combination of intensive advising, enforced implementation of intervention plans and economic pressure.