A fixed dosage regimen of voriconazole is routinely used for prophylaxis of aspergillosis in lung transplant patients at our institution. We hypothesize that use of a fixed dosage voriconazole regimen leads to large degree of variability in drug exposure among lung transplant patients and consequently, therapeutic failures or toxicity. This is a three part study which will examine plasma and lung voriconazole concentrations achieved with the prophylactic regimen and assess for a correlation between these concentrations with efficacy and toxicity. We aim to conduct an initial pilot study in 12 lung transplant patients to characterize the pharmacokinetic profile of voriconazole with both intravenous and oral doses. The data gathered from the pilot pharmacokinetic study will then be utilized to correlate trough concentrations with total voriconazole drug exposure as measured by area under the plasma concentration versus time curve (AUC). Additionally, trough concentrations will be followed over nine weeks of the prophylactic treatment period in a larger cohort of patients to determine maintenance of consistency in trough concentrations and whether the plasma concentrations are predictive of efficacy and toxicity. Voriconazole lung concentrations will be measured in a pilot study of 12 patients who undergo a bronchoscopy procedure as part of their standard medical care in order to determine the relationship between plasma and lung concentrations. The information obtained from this three phase study will be utilized to characterize the pharmacokinetics of voriconazole in lung transplant patients. Further, it will be used to define an optimal therapeutic voriconazole regimen that will be individualized to target specific concentrations in the lung and plasma to maximize efficacy and minimize toxicity