Sexually transmitted diseases (STDs), including urethritis caused by gonococcus and Chlamydia trachomatis, are of increasing public health importance. The common occurrence of coinfections and the emergence of antimicrobial resistance of both pathogens emphasize the need for a single broadly active drug for management of these STDs. Penicillins and other beta-lactam agents effective against susceptible gonococci are ineffective against chlamydia. However, fluoroquinolones and macrolides provide broad coverage for both pathogens, but the emergence of gonococcal resistance within these classes limits their utility. Early descriptions of the in vitro spectrum of activity of fusidic acid indicated the susceptibility of a limited number of Neisseria gonorrhoeae isolates (MIC range of 0.40 to 0.89 g/ml). This report examines the in vitro susceptibility of recent isolates of N. gonorrhoeae and C. trachomatis to fusidic acid (CEM-102; sodium fusidate), a potential alternative therapy for use in this clinical setting. Thirty-five clinical isolates of N. gonorrhoeae collected in the United States, Asia, and European medical centers since 2005 were tested using reference agar dilution methods per the Clinical and Laboratory Standards Institute (CLSI) M07-A8 and M100-S20 documents. Ten isolates of C. trachomatis, including standard isolates from the ATCC and recent clinical isolates, were selected for study with susceptibility testing performed via cell culture using HEp-2 cells. The MIC90 of fusidic acid against N. gonorrhoeae isolates was 1 g/ml, and it was active against all strains at 2 g/ml. Against C. trachomatis, fusidic acid had an MIC range of 0.12 to 0.5 g/ml with identical MIC90 and MBC90 values of 0.5 g/ml. These in vitro testing data suggest that fusidic acid may be considered an alternative treatment for multidrug-resistant N. gonorrhoeae strains and could provide an advantage for treatment of STD as a single agent targeting both gonococcus and C. trachomatis. However, fusidic acid urinary tract concentrations are limited, and further investigations are needed to determine its potential role for STDs caused by these two pathogens.