FIELD : medicine.SUBSTANCE : invention relates to medicine, namely, to devices for fixing medical instruments during surgery. Stereotactic tool holder consists of the lower and upper segments, the lower segment nut, the upper segment nut, the upper segment washer, the lower segment sleeve, the upper segment sleeve. Lower segment is made in the form of an arc-shaped support element with a longitudinal slot. Nut of the lower segment is formed from one end with a notch for placement in the slot of the support element of the lower segment, and on the other side with the protruding collar. Upper segment is made in the form of an arc-shaped support element with a longitudinal slot to accommodate the sleeve of the upper segment. Bushing of the lower segment has an axial hole for the adapter, one end of the bead is for emphasis in the lower segment, the other end is a flywheel and the outer threaded portion for the nut of the lower segment is adjacent to the collar. Upper segment sleeve has an axial hole for the lower segment sleeve, an external threaded portion for the nut and an upper segment washer, and at one end a portion with an enlarged outer diameter made from the butt end of the lower segment nut. Stereotaxic medical tool holder adapter according to the first embodiment is made with at least one of the through holes located in the inner adapter member having a lead insert. Adapter of the second embodiment is made with a conical end. Adapter of the third variant consists of a sleeve and a core rigidly pressed into it with grooves at the edges.EFFECT : use of inventions makes it possible to improve the accuracy of guidance of a medical instrument, expand the scope of application, and reduce the amount of material used.4 cl, 16 dwg