Collective dose for cardio-angiography studies is the highest of all non-CT radiological investigations. Deterministic effects such as erythema, epilation and ulceration being reported on patients who have undergone these procedures emphasise the importance of optimising radiation dose, whilst not compromising diagnostic efficacy. This study investigated radiation doses delivered to patients for four common types of cardiac radiological examinations: coronary angiography (CA), percutaneous coronary intervention (PCI), coronary angiograms (which were followed by an interventional procedure (CA-PCI)) and permanent pacemaker insertions (PPIs). 21 cardiac imaging suites participated in the study in 14 hospitals, representing 90% of relevant centres within Ireland. Radiation dose was monitored for 1804 adult patients using dose-area product meters. Operational and examination details, such as cardiologist grade, patient details, examination complexity and exposure factors, were recorded for each examination. Variation factors in dose between centres ranged from 2.7 to 11.1, but these factors were not higher than intrahospital variations previously recorded for other examinations within Ireland, such as chest X-ray. High-dose centres were often associated with long screening times, a high patient body mass index and complexity of the procedure. Preliminary dose reference levels (DRLs) were established using rounded third quartile values at 4200 cGy cm(2), 8400 cGy cm(2), 10 700 cGy cm(2) and 2100 cGy cm(2) for CA, PCI, CA-PCI and PPI, respectively. With these commonly performed relatively high-dose procedures, it is important that some guideline values are available to encourage optimised strategies. These proposed DRLs offer such guidance.