The capacity of a new optical navigation device is demonstrated by six microsurgical procedures for small subcortical lesions within the central sensorimotor strip. This small series is aimed at less invasive resection in this functionally critical region, independently of primary diagnosis and outcome. Guided by high resolution CT imaging data five brain tumours and one cavernous angioma was selectively located and most sparingly removed without additional sensorimotor deficit. In two cases improvement of a pre-operative paresis was observed immediately after surgery. Thanks to light-weight freehand pointing instruments and a ranging accuracy of +/- 1 mm, damage to functionally important brain areas and vessels was avoided by using uncommonly oblique, e.g., transsulcal ways of access which would hardly have been possible even with guidance by conventional stereotaxy. The demanding systematic cortical stimulation of the precentral gyrus applied in three cases was only sensitive in infiltrating tumours-e.g., low grade astrocytomas-where for want of adjuvant therapy it was essential to proceed to the extreme limits of resection. In general, precise anatomical localisation by computer aided surgery (CAS) is sufficient in small central lesions which guarantees minimally invasive surgery. The potential of this new, soon commercially available optical navigation system in (neuro) surgery, quality control and teaching is discussed.