A hand-held, manually operated pipetter having a variable volume controlled by a rotating spindle (76) and adjusting screw (48) that control the position of a stop (70) which limits the upper end of the stroke of the pipetter piston (53). The lower end of the stroke is controlled by a movable stop (80) urged to a first position by a blow-out spring (114) which may be overcome with additional force applied to the pipetter piston (53) when the lower stop (80) is engaged. The pipetter also includes a stripper (181) which surrounds the tip holder (26) and which is actuated by a rod (152) movable in the body (20) of the pipetter along a path parallel to the path of the pipetter piston (53). The pipetter piston (53) and the stripper rod (181) are controlled by separate actuators (58, 154) which may readily be engaged by the thumb of the hand which holds the body (20) of the device.
