In Thai population , there are different genetic polymorphism from Caucasian ,resulting in a different response to the initial dose and there is limited resources in Thailand , mostly patients are unaccessible for Voriconazole level. Especially,in the period of starting drug, which is the critical period for patients ,most of them are post chemotherapy which may have gastrointestinal problems, mucositis , vomiting or diarrhea ,as well as receiving multiple concurrent medications. All of these affect drug absorption,drug level and efficacy of treatment. Thus, this study was designed to evaluated Voriconazole level in Thai patients in the first two week after administration.