The National Guidelines for Health Planning require 300 cardiac studies per year in cardiac catheterization laboratories for adequate economic use and safety. To study how these guidelines would affect existing laboratories, data were collected on the cost of coronary angiography and use of all cardiac catheterization laboratories in Washington. The average cost of coronary angiography was $1,363, with the total cost affected by the duration of hospital stay, cardiac laboratory charges, and professional fees. Total angiographic use ranged from 293 to 791 studies per room, but eight laboratories did not perform 300 cardiac studies during 1977. Health planners recommend high use rates based on the theory that there is an inverse correlation between the number of studies and cost. In this study, the regression equation showed no fall in charges with increased number of studies. Therefore, while it may be reasonable from an economic point of view to expect 300 angiographic cases per year in existing laboratories, there is no economic justification for requiring a certain number of cardiac studies per year.