An acute salimonycin poisoning was diagnosed in a pig farm, in this case in one compartment housing 200 weaning piglets. The poisoning was caused by a drug incompatibility due to the administration of salinomycin in the feed and the presence of traces of tiamulin left in the drinking water, resulting from the fact that tiamuylin had been administered to fattening pigs housed in the stable four months before the appearance of the clinical symptoms in the piglets. The main symptoms of poisoning were loss of appetite and locomotor disturbances. The locomotor symptoms consisted of weakness of the posterior body half and lateral decubitus in more severe cases. Finally, 35 of the 200 piglets died. Histological study of the skeletal muscles, biochemical study of the blood, and chemical analysis of the drinking water for tianulin were performed to establish the diagnosis.