A method for detecting contact of the tip of a pipetting needle with a liquid contained in a vessel, said detecting being effected within a time interval during which the pipetting needle is moved towards said liquid in said vessel for performing a pipetting operation, said method comprising (a) applying ultrasonic pulses to the pipetting needle by means of an electromechanical transducer which is mechanically connected to a part of the needle which is located at a predetermined distance from the tip of the pipetting needle, (b) transmitting through the pipetting needle mechanical pulses generated by the application of said ultrasonic pulses to said pipetting needle through a coupling member mechanically connected to the needle and to the electromechanical transducer, said coupling member being connected to a part of the needle which is located at a predetermined distance from the tip of the pipetting needle, (c) said transmitting of mechanical pulses including transmission of mechanical pulses generated by said transducer towards the tip of said pipetting needle and also transmission in the opposite sense of mechanical pulses reflected at said tip, wherein said coupling member selectively transmits to the electromechanical transducer a selected wave component of ultrasonic echo waves reflected at the tip, (d) receiving said reflected mechanical pulses with said electromechanical transducer, said electromechanical transducer thereby generating a corresponding electrical output signal, and (e) monitoring said electrical output signal, selecting at least one specific component thereof by means of a time-of-flight or signal phase analysis, and by evaluating the variation with time of predetermined characteristics of a parameter of said at least one selected component of said output signal in order to detect the position of the needle at which the pipetting needle contacts the free surface of said liquid contained in said vessel and for providing a resulting signal representative of the result of said evaluation. (a) applying ultrasonic pulses to the pipetting needle by means of an electromechanical transducer which is mechanically connected to a part of the needle which is located at a predetermined distance from the tip of the pipetting needle, (b) transmitting through the pipetting needle mechanical pulses generated by the application of said ultrasonic pulses to said pipetting needle through a coupling member mechanically connected to the needle and to the electromechanical transducer, said coupling member being connected to a part of the needle which is located at a predetermined distance from the tip of the pipetting needle, (c) said transmitting of mechanical pulses including transmission of mechanical pulses generated by said transducer towards the tip of said pipetting needle and also transmission in the opposite sense of mechanical pulses reflected at said tip, wherein said coupling member selectively transmits to the electromechanical transducer a selected wave component of ultrasonic echo waves reflected at the tip, (d) receiving said reflected mechanical pulses with said electromechanical transducer, said electromechanical transducer thereby generating a corresponding electrical output signal, and (e) monitoring said electrical output signal, selecting at least one specific component thereof by means of a time-of-flight or signal phase analysis, and by evaluating the variation with time of predetermined characteristics of a parameter of said at least one selected component of said output signal in order to detect the position of the needle at which the pipetting needle contacts the free surface of said liquid contained in said vessel and for providing a resulting signal representative of the result of said evaluation.