A retrospective review was undertaken of 90 patients admitted to the cardiothoracic intensive care unit and who comprised 47% of all transvenous implantable cardioverter defibrillator operations performed between March 1991 and August 1995. The review aimed to evaluate the necessity for routine postoperative intensive care unit (ICU) admission after implantable cardioverter defibrillator operation. Pre-, intra- and postoperative data were analysed. Eight of 90 patients (9%) subsequently required care unique to the ICU. None of the variables examined, including the Acute Physiology Score (APACHE II system), was helpful in identifying patients who required unique ICU services. Patients undergoing transvenous implantable cardioverter defibrillator surgery are identified as a low risk group requiring in over 90% of cases monitoring services rather than active therapy in an ICU. As no reliable predictors seem to exist to identify the necessity for postoperative ICU admission, cardioverter defibrillator implantations should only be performed in hospitals where adequate facilities are readily available.