A method for performing an in-vivo calibration of a blood pressure sensor that is associated with an in-vivo balloon system. The method involves monitoring a patient's blood pressure by observing the system gas pressure while at the same time monitoring the patient's blood pressure through the sensor. The blood pressure measurements obtained by monitoring the system gas pressure are used as reference, or “true,” blood pressure measurements, and an “offset” is determined between the reference blood pressure measurements and the blood pressure measurements obtained through the sensor. The offset can be stored in a memory, which may also store sensor sensitivity data. The offset and/or sensitivity data may be used to adjust future measurements obtained from the sensor, thereby generating calibrated sensor measurements.