This article describes how cognitive theory can be applied to the testing and teaching of intelligence. The article is divided into three main parts. The first part describes how the study of intelligence, traditionally an area that has been viewed as under the purview of differential psychology, has come squarely into the purview of cognitive psychology. The second part describes how the testing and teaching of intelligence, which in the past have been largely atheoretical, have been transformed into theoretically based enterprises guided by the theories of cognitive psychology. The last part describes a particular theory of intelligence, the triarchic theory, and how it has been applied to the problems of testing and teaching intelligence. It is concluded that cognitive psychology has given the study of intelligence a ‘new lease on life’, and that the testing and teaching of intelligence can and should be viewed as a primary focus of application for the principles of cognitive psychology.