Although posaconazole is approved for the prophylaxes and treatment of invasive fungal infections, specific dosing guidelines for posaconazole in (morbidly) obese patients are not specified. There is clear evidence indicating that heavier patients are receiving a sub-optimal dose if the current guidelines are used. Specifically in the setting of augmented prevalence of species with intermediate susceptible to posaconazole, adequate dosing is needed at start of treatment.