Abstract
Standardization of enzyme measurements grew out of an unsatisfactory situation in the late 1960's. More national and regional professional groups began a process based on standardization of methodologies. Experiences from these national efforts were utilized by the International Federation of Clinical Chemistry as part of a development of international reference methods. Based on these modified routine methods were suggested and implemented. A last brick in the system is the production of certified reference materials. Together these components comprise a consistent system for measurement of the catalytic activity of enzymes.