A defibrillator (30) with an automatic self-test system (42) that includes a test signal generator and a defibrillator status indicator. The test system (42) preferably performs functional tests and calibration verification tests automatically in response to test signals generated periodically and/or in response to predetermined conditions or events and indicates the test results visually and audibly. The invention also relates to a method for automatically determining and indicating a defibrillator's status without human intervention.