Because arterial cannulation assists in management of critically ill patients (pts), we assessed the utility of extending intra-arterial monitoring to hospitalized patients suffering in-hospital cardiopulmonary arrest outside of intensive care wards. A totally self-contained, readily portable system for rapid insertion of emergency intra-arterial lines was evaluated in 16 pts from 53 to 89 years old (mean = 66.5 years) undergoing cardiopulmonary resuscitation. Cannulation was successful in 14 pts (88% success rate). In 8 of 14 pts, cannulation was achieved rapidly and efficiently, whereas in six it was slightly delayed, once due to technical problems and five times due to difficulty cannulating the vessel. In addition to providing continuous pressure monitoring and ready access to arterial blood samples, direct feedback from the intra-arterial pressure waveform frequently led to improved compression technique by the resuscitator performing external cardiac massage. We conclude that under selected circumstances emergency intra-arterial monitoring has a potentially important adjuvant role during cardiopulmonary resuscitation.