The standard procedure for left anterior descending (LAD) coronaryartery bypass requires a sternum split. The internal mammary artery(IMA), most typically the left one (LIMA), is dissected free frombehind the sternum and is then anastomosed onto the heart below theocclusion of the LAD. Totally Endoscopic Coronary Artery Bypass(TECAB) is a less invasive alternative to the standard procedure. Thisprocedure results in heavily reduced invasiveness, but also leads toloss of precision, reduced force feedback and loss of overview. Thepurpose of this work is to alleviate the problems related to loss ofoverview by generating an augmented reality for the surgeons in whichthey are given the impression of 'seeing through' the tissuessurrounding the LIMA thus making localization of the LIMA a simplematter. Using preoperative CT or MR data, the LIMA is located withrespect to the tissues surrounding it. Intra-operatively tissuessurrounding the LIMA are tracked using a stereo endoscope held by arobotic arm (AESOP). Knowing the position of the endoscope relative tothe visible surface inside the chest cavity now makes it possible tocalculate where in the endoscopic video stream the LIMA islocated. Positioning of the endoscope is also possible using anoptical tracking system. This information is then used to generate anaugmented reality where the LIMA is superimposed on it's correctposition in the video stream. The thesis is using artificial models totest and experiment on the described problem.