The benefits of mobile cardiac catheterization laboratories include keeping patients closer to their families, communities, local hospitals, and primary care physicians while receiving services comparable to those available at tertiary centers. However, there are very few studies regarding the safety of performing cardiac catheterization in mobile laboratories at remote locations. Thus, the authors performed an observational study of 1,775 consecutive patients undergoing a diagnostic cardiac catheterization in a mobile catheterization laboratory at primary care hospitals served by the Appleton Heart Institute (AHI) from August 1, 1991, to December 31, 1998. Twenty-three percent (1,775/7,637) of all AHI diagnostic cases in this time period were performed in the mobile catheterization laboratory. Urgent transfer to the tertiary care facility via ambulance or helicopter was used for 2.3% of patients (n=41). The overall complication rate was 1.2% (n = 21). Of the patients who underwent cardiac catheterization in the mobile laboratory, 32.6% (n = 579) were subsequently referred for interventional or surgical revascularization. There were no deaths. Cardiac catheterizations can be performed safely in a mobile laboratory at primary care hospitals, provided that immediate transfer is available for those in need of urgent intervention or revascularization and that unstable patients are not studied in the mobile laboratory.