florfenicol administered through the drinking water has been recommended as a metaphylactic antibacterial drug to control outbreaks of respiratory diseases in pigs caused by strains of actinobacillus pleuropneumoniae and pasteurella multocida yet it is difficult to pinpoint in practice when the drug is given metaphylactically or therapeutically. Further,pigs are likely to reject florfenicol-medicated water,and plasma concentrations of the drug are likely to be marginal for diseases caused by escherichia coli,klebsiella pneumoniae, and staphylococcus aureus. The reported minimal inhibitory concentration (MIC) values for these organisms show a breakpoint of 2 to 3