To investigate pharmacokinetics(PK) and pharmacodynamics(PD) of Caspofungin in ICU patients after received a loading dose of 70mg followed by 50mg (35mg if Child-Pugh score is 7-9), 40 patients will be recruited. Blood samplings for PK analysis will be collected on day 4 in this study. Caspofungin plasma concentrations are measured by using solid phase extraction and reverse phase high-performance liquid chromatography. Safety analyses will be taken daily during the treatment of Caspofungin. Tests for drug tolerance of fungi and efficacy assessment (clinical and mycological responses) will be taken every 3 days by clinical and mycological tests.

Inclusion Criteria:

• Patient is admitted to ICU with APACHE-II score more than 15
• Subject is 18 years old and older on the day of the first dosing
• Subject with evidence of proven or probable IFI defined by modified criteria of European Organization for Research and Treatment of Cancer(EORTC)

Exclusion Criteria:

• patient is known to be hypersensitive to caspofungin
• patient's Child-Pugh score is more than 9
• patient is prone to discontinue treatment result from lack of cost
• patient or their guardian refuse to sign a informed consent form
• patient concurrently receiving efavirenz, nevirapine, rifampin, systemic dexamethasone, phenytoin, carbamazepine, phenobarbital, or cyclosporine and other agents have influence on PK parameters of caspofungin
• patient is treated with caspofungin within 24 hours