THERE have been several reports recently on the use of fusidate sodium in the treatment of infections caused by Staphylococcus aureus.1 One of the most difficult problems in the evaluation of any new antimicrobial agent is to find suitable situations in which to assess the efficacy of the drug. The optimal situation is one in which the only active therapy is the agent under study. Bacteremia (endocarditis) and pneumonia are two disease states which lend themselves readily for clinical testing of drugs. Most chemotherapeutic agents (with the exception of some specifically for the urinary tract or skin) have been accepted or rejected on their ability to cure or improve these infections. In the therapy of surgical microbial diseases, clinical evaluation of efficacy is much more complex. The majority of the cases represent a localization of purulent material some place in the body. In these situations incision and drainage of