A method for drawing a biological sample using a suction-discharge device, such as a manual or automatic pipette, built into an automated device or not. A method for detecting the free surface of a biological sample and/or solid, a sample drawing device such as a pipette and a device for detecting the free surface of a biological sample or a solid are also disclosed. This method includes actuating a means causing a pressure variation or an air flow within the suction-discharge device, positioning the lower free end of the device in such a way so that it becomes flush with a free surface of the biological sample, measuring an overpressure within the suction-discharge device, and sampling a quantity of the sample by suction using the device. The invention finds a preferable application in the field of automatic analyzers.