Arterial catheterization for hemodynamic monitoring is used widely in clinical management. Complications of connulation have been recognized since introduction of the technique. This review examines radial, brachial, axillary, and femoral cannulation sites. Waveform distortion, adjacent structure injury, and the incidence of thrombus are described. Computerized subject heading searches were executed using CINAHL and MEDLINE databases. Searches encompassed English-language, randomized, controlled trials, reviews, practice guidelines, and meta-analyses published from January 1997 to February 2002. Additional studies were identified via review of retrieved literature. Radial cannulation is subject to inaccuracy and thrombus formation, although a benefit is dual circulation. The brachial site is subject to inaccuracy, lacks collateral circulation, and is associated with median nerve injury. Axillary cannulation provides data closely approximating aortic pressure and poses minimal thrombotic risk but is associated with brachial plexus compression. Femoral cannulation provides a pulse contour approximating aortic with minimal thrombotic risk. There is little evidence to show increased incidence of catheter-related systemic infection at this site.