for identifying disproportionate risks and outcomes, this broad level of epidemiological analysis rarely proves useful in identifying the relevant characteristics that best define the audiences for a health campaign. This is because any single group characterized by these broad demographic variables is actually composed of multiple diverse segments with different needs, experiences, attitudes, and behaviors.

To address the heterogeneous nature of populations, health communication programs have applied the marketing concept of segmentation. Segmentation is the process of partitioning a heterogeneous population into subgroups or segments of people with similar needs, experiences, and/or other characteristics. A number of approaches have been developed to help determine optimum audience segmentation. Segmentation assumes that audiences that perceive a message as relevant to their interests, concerns, and problems are more likely to pay attention to the message, to process it deeply, and to remember and act on it, than are audiences that do not perceive the message as personally relevant. An elaboration of these concepts is provided in the following paragraphs.

A sensible communication campaign recognizes heterogeneity in its population. First, all members of the population do not have the same status with regard to a behavior. For a youth tobacco prevention campaign, some youth are already heavy smokers, some smoke irregularly, some have smoked in the past but have quit, and some have never smoked but are intrigued and at higher risk of beginning to smoke, while others have never smoked and, regardless of a campaign, are very unlikely to become smokers. Each of these segments of the youth population may require different interventions. The behavioral objective for the heavy smokers may be enrollment in a cessation intervention; for the casual smokers, it may be stopping all smoking; for the prior quitters, it may be developing skills to resist cigarettes in situations that signal smoking temptation; for the intrigued nonsmokers, it may be resisting offers of cigarettes from peers; and for the committed nonsmokers, it may be reinforcing their existing preference. One campaign might choose only one of these audience segments as its target, or at least