In a finishing herd of 1020 head clinical salmonellosis was a problem in market age pigs during 2002. During two years, intervention and prevention was done using organic acids through drinking water and feed. Progress of the Salmonella-status was monitored by detecting antibodies against Salmonella. From this case it can be concluded that clinical salmonellosis disappeared and dead loss decreased rapidly after application of the acids. The mean OD% dropped strongly from 40 to below 10. The herd never became entirely Salmonella-free, defined as no samples with OD%>10. The sickbay was a problem location because it was not operated on an all-in/all-out basis. Infection levels differed strongly between stables and compartments. The outbreak in the third quarter of 2002 cost on average 4.60 per pig delivered to the abattoir in that period. The majority of the costs of clinical salmonellosis are due to a reduction of technical results.