Inclusion Criteria:  Patient older than 18 years. The subject has stable or unstable angina pectoris, or a positive functional study for ischemia. The subject is eligible for PCI. The subject gives consent prior to study inclusion. The subject has a calcified lesion that does not dilated fully after balloon angioplasty at 16atm with a ≥2.5mm non-compliant balloon. The calcified lesion has a 50-90% diameter stenosis by angiographic assessment.  Exclusion Criteria:  Previous and/or planned brachytherapy of target vessel. Pregnant and/or breast-feeding females or females who intend to become pregnant. Patients who intend to have a major surgical intervention within 6 months of enrolment in the study. Patients who previously participated in this study. Subject has experienced an acute myocardial infarction 72 hours prior to the index procedure, as defined either by the presence of a new Q-wave in 2 or more contiguous leads, or by a CK greater than two times site upper reference limit (URL) with presence of CK-MB greater than the site URL. The subject has suffered a stroke or transient ischemic neurological attack or cerebrovascular accident within the past six months, or has any known intracranial mass, arteriovenous malformation, aneurysm or other intracranial pathology. The subject has experienced a significant gastrointestinal or genitourinary bleed within the past six months, or has had any active bleeding within two months. Planned revascularization of target vessel within 1 year after index procedure. Lesions not ideal for Shockwave treatment: Longer than 40mm. The target vessel contains intraluminal thrombus. The subject has had a prior stent in the target lesion, including a 5mm zone proximal and distal to the lesion.