Abstract: Pipette with adjustable volume of aspirated liquid built of a handle (1) and of a nozzle (3) and of coupled with them: an exchangeable pipette tip ejection mechanism, a drawing up and discharging mechanism with a plunger (12) arranged in said pipette nozzle (3), a plunger working stroke adjustment mechanism with at least one driving member (16), a manually actuated lock mechanism locking a drive assembly of an adjustment screw of a plunger working stroke, an engaging mechanism which engages said plunger working stroke adjustment mechanism with a counter (14) of an aspirated liquid volume by said pipette, a calibration mechanism for a change of a pipette calibration coefficient, whereas said driving member (16) of said drive assembly of said adjustment screw of the plunger working stroke is accessible from outside through at least one window (38) in a wall of said handle (1), said pipette is characterised in that said lock mechanism of said drive assembly of said adjustment screw of the plunger working stroke