The ability to isolate and accurately position single cells in three dimensions is becoming increasingly important in many areas of biological research. The authors describe the design, theoretical modelling and testing of a novel dielectrophoretic (DEP) tweezer for picking out and relocating single target cells. The device is constructed using facilities available in most electrophysiology laboratories, without the requirement of sophisticated and expensive microfabrication technology, and offers improved practical features over previously reported DEP tweezer designs. The DEP tweezer has been tested using transfected HEI-193 human schwannoma cells, with visual identification of the target cells being aided by labelling the incorporated gene product with a green fluorescent protein.