Abstract: Instrument (9) micro positioning device on the stereotactic system consists of the linear drive with the collet-chuck and the bracket (1) with the instrument (9) guide. The collet-chuck fixes and positions the instrument (9) with the collet (6a, 6?a) and associated taper-nut (7, 7?). The collet (6a) with the associated nut (7) is intended for clamping and positioning a single instrument, whilst the collet (6?a) with the associated taper-nut (7) is intended for the simultaneous securing and positioning of five instruments (9) or microelectrodes at a time. Through holes of the collet (6?a) are coaxial with bores of the central spacer as instrument positioning guide (9), where the sections of the collet (6?a) form and define the four through holes, which are symmetrical and evenly-spaced around the central through-hole.