A number of pipetting aids are commercially available which obviate the necessity of filling pipets by oral suction. Most of the commercially available devices involve fitting the pipet into a soft tight fitting bushing and filling by means of either a piston or a rubber bulb. The pipet is then emptied by means of a valve control which permits, it is claimed, a dispensing accuracy of 0.1mL. It is at once apparent that the probable error (10% for a 1 mL. pipet) is considerably greater than is permissible for great precision. In practice these devices are found to be awkward and after a period of use tend to become even more so due to corrosion of the valve and aging of the rubber bushing and rubber bulbs.