A case of a 44-year-old woman presenting pulmonary edema secondary to posterior fossa meningioma is reported. The authors have tried to demonstrate the relationship between a lesion occupying space in the posterior fossa and important pulmonary abnormality such as interstitial edema based on increasing A-aD02 (oxygen alveolar arterial gradient) in this peculiar case. A-aD02 is easily measured and represents a good guide for evaluating the efficiency of medical and neurosurgical management when it is done in the serial way, particularly in those cases of non cardiogenic pulmonary edema.