The merits of generalizability theory in the formulation of construct definitions and in the determination of reliability estimates are discussed. The broadened conceptualization of reliability brought about by Cronbach's generalizability theory is reviewed. Career Maturity Inventory data from a sample of 60 ninth grade students is used to demonstrate the power of the technique to estimate reliability coefficients for a number of differing measurement procedures. It is concluded that researchers frequently use reliability coefficients that are inflated estimates of the precision with which their constructs are being measured. (Author/GK)