This study was designed to evaluate the implantation of internal cardioverter/defibrillators under local anaesthesia by electrophysiologists and to compare this to our former experience of implants with general anaesthesia. Forty-seven internal cardioverter/defibrillators were implanted at our institution by electrophysiologists. Twenty-nine operations were performed under general anaesthesia (isoflurane 0.4-0.6%), and 18 under local anaesthesia (mepivacain 1%). The defibrillator leads were introduced by venotomy of the cephalic vein (n = 25), puncture of the subclavian vein (n = 17) or both (n = 5). All devices were implanted beneath the pectoral muscles. The mean operation time was 99 +/- 29 min. In the group with local anaesthesia the operation time was significantly shorter than with general anaesthesia (86 +/- 20 min vs 107 +/- 31 min; P = 0.027). The defibrillation threshold with biphasic shock application was below 24 J in all patients; thus, the implantation of an additional subcutaneous patch electrode was unnecessary. There were no major complications in either group. However, modifications were required in four patients: in one a set screw had to be re-tightened after delivery of an erroneous shock in the early postoperative phase; in another, device migration occurred several weeks after implantation, but no therapeutic intervention was required; in another, a rise in pacing threshold and partial sensing loss were noted ten days postoperatively; in the fourth, a minor pneumothorax occurred after subclavian puncture, but no further treatment was necessary. There was no intra-operative or postoperative mortality in either group. Implantation of internal cardioverter/defibrillators under local anaesthesia and mild sedation is feasible, and can be safely performed by electrophysiologists experienced in basic surgery. The newly developed smaller devices allow implantation in the subpectoral region, and with "active can' configuration and biphasic shock application, subcutaneous patch electrodes become unnecessary.