Invasive fungal infections, predominantly aspergillosis and candidiasis are the most important causes of morbidity and mortality in immuno-compromised patients. Antimycotics are used for the treatment and prophylaxis of fungal infections. Antifungal drugs show large intra- and interindividual variabilities in pharmacokinetics, thus, the accurate measurement of the individual drug concentration in serum/plasma is essential for therapy control and success.