Over the past 2 years at the Montreal Neurological Institute and Hospital, we have evolved an integrated environment for the planning of stereotactic procedures, based on images from magnetic resonance imaging, digital subtraction angiography and computed tomography modalities. These procedures rely on fiducial marker sets which are attached to our 'OBT' stereotactic frame, and which may be recognized in the images. The software package is modular and operates in both minicomputer (PDP-11 and VAX) and IBM personal computer environments. In addition to routine tasks for stereotactic planning, the package also supports dosimetry planning for stereotactic radiosurgery.