The construct of involvement, used by marketers and consumer behaviorists for many years as a predictive measure of the qualitative relationship between an individual and a stimulus, has long been defined as having affective or cognitive roots. However, definitions that favor one or the other too heavily are less helpful because they are too restrictive. An affective definition of involvement, used primarily by social psychology researchers, asserts that involvement is an enduring drive state that is attached to one's central values or ego. A number of researchers have attempted to measure this in relation to subjects' involvement with products or ideas, but learning models that show cognitions preceding attitude formation suggest this theory is not very useful. Cognitive studies of involvement have looked at the influence of involvement on attention, comprehension, and behavior, as well as on persuasion. H. Krugman's work with "bridging experiences," M. Ray's work with product differentiation, and A. Mitchell's refining of the cognitive definition to include attention and interest have proven illuminating, but research indicates that the distinction between affective and cognitive measurement is not clear. A definition that includes both types of measures encompasses comprehension, emotions, attitudes, and behaviors. Measures of interest and attention, and measures of emotional involvement can be used to assess the level of individual involvement. (A diagram and thirty-four references are included.) (JC)