The currently recommended dosage regimen of caspofungin (50 mg/day) was developed for patients with invasive candidiasis. With invasive aspergillosis, successful outcomes occur in less than half the patients. We evaluate the pharmacokinetics in a patient with elevated liver enzyme levels after liver transplantation, who received caspofungin for the treatment of aspergillosis. Plasma concentrations of caspofungin were monitored at 2 different dosage regimens. The area under the concentration-time curve (AUC) at a dosage of 70 mg was 191 mg h/L and was associated with an increase in liver enzymes. After dose reduction to 50 mg with an AUC of 100 mg h/L, liver enzymes normalized. In conclusion, caspofungin plasma concentrations may be helpful to evaluate exposure and reduce the need for off-label dosing.