Abstract: An apparatus and method for leak testing a lumened instrument, such as an endoscope, utilizes a compressor for pressurizing the interior of the lumened instrument to a predetermined internal pressure and a monitoring device which de-actuates the compressor when the internal pressure reaches the predetermined internal pressure. Calculator circuits calculate any difference in the instrument pressure between the moment that the compressor is de-actuated and the end of a prescribed period of time following the de-actuation of the compressor, and comparison circuits compare the pressure difference to an acceptable range of pressure differentials. A set of pass/fail indicator lights provide a visual indication of whether the compared difference is within or outside of the acceptable range so that an operator can tell by viewing the pass/fail indicator lights whether the instrument being tested has an unacceptable leak.