THREE METHODS OF COST-EFFECTIVENESS ARE DISCUSSED--USE OF COMPUTERS, MATHEMATICS, AND EXPERTISE. THE USE OF EXPERTISE IS EMPHASIZED. THE DISCUSSION ON EXPERTISE JUDGMENT IS BASED ON PAPERS BY O. HELMER, WHICH ILLUSTRATE THE DELPHI METHOD OR CYBERNETIC ARBITRATION. ALTHOUGH COMPUTER AND MATHEMATICAL ANALYSIS (PARTICULARLY GAME THEORY) ARE BECOMING INCREASINGLY SIGNIFICANT IN COST-EFFECTIVENESS ANALYSIS, IT IS THE AUTHOR'S OPINION THAT FOR COMPLEX QUESTIONS, INTUITION AND JUDGMENT MUST CONTINUE TO SUPPLEMENT SYSTEMATIC ANALYSIS. THIS PAPER WAS PREPARED FOR PRESENTATION DURING THE SHORT COURSE, "COST EFFECTIVENESS, THE ECONOMIC EVALUATION OF ENGINEERED SYSTEMS" (UNIVERSITY OF CALIFORNIA, LOS ANGELES, MARCH 27-31, 1967) AND IS AVAILABLE AS AD 650 129 FROM CLEARINGHOUSE FOR FEDERAL SCIENTIFIC AND TECHNICAL INFORMATION, CAMERON STATION, SPRINGFIELD, VIRGINIA 22314, FOR $3.00 HC, $0.65 MF. (HW)