Audience segmentation is widely regarded as essential to effective health communication campaign efforts. Nonetheless, its practice is typically ad hoc. The conceptual history and theoretical bases for audience segmentation are reviewed, and typical audience segmentation strategies for health communication efforts are described and critiqued. An analogy is drawn between the methodological problems associated with audience segmentation and those of multivariate classification and taxonomy in botany and zoology. Cluster analytic techniques responsive to these issues are described, as are applications of these techniques for analysis of health communication campaign audiences. Approaches that would permit widespread use of such segmentation strategies are discussed, and recommendations for such efforts are made.