Fusidic acid is an active agent against a wide variety of gram-positive bacteria, and it has been increasingly used in methicillin-resistant Staphylococcus aureus infection. The major adverse effects are mild gastrointestinal discomfort and diarrhea. The hematological side effects such as granulocytopenia and thrombocytopenia have been rarely reported in western countries, but have not been documented in Asian population. Between January and April 2001, we identified 2 cases of fusidic acid-induced leukopenia and thrombocytopenia after 2 weeks of fusidic acid treatment. In both cases, hematological abnormality resolved in 3 to 6 days after discontinuation of fusidic acid. The published literature regarding hematological adverse effects caused by fusidic acid is reviewed in this report, and an immune-mediated mechanism possibly by drug-dependent antibody is speculated. We recommend periodic complete blood count check in patients receiving long-term fusidic acid treatment to avoid serious hematological adverse effects.