One of the additional methods of coronary artery assessment is intravascular ultrasound (IVUS). Contrary to coronary angiography this relatively new technic provides new information including precise calculations of stenosis degree, morphology of atheromatous plaque and differentiation of its structure. Coronary angiography was performed in 54 years old male patient with unstable angina, revealing 99% stenosis in distal RCA. Discrepancy between clinical presentation and angiographic findings and exercise test resulted in performing IVUS of LAD. Angiographically clear LM and LAD were found to be narrowed 52% and 58% on IVUS. Subsequent CABG resulted in symptoms withdrawal and increase of physical tolerance. Exercise test after CABG did not reveal ischaemia in area of LCA at 10 METs. IVUS is found to be an important technic in assessment of silent or ambiguous lesions and in many cases allows to choose the optimal method of treatment of coronary artery disease.