Addressing the dynamic and integrative nature of the world's press systems, this paper presents a comprehensive press theory and accompanying model. Three "primary motives"--survival, ideology, and market--are posited as determinants of press systems, using the nation state as the unit of analysis. The premises of the paper are: (1) press behavior and values are determined and identified as primary motives which are shared by society, government, and other national institutions; (2) nations and their press systems subscribe to three primary vocabularies of motive, one of which predominates at any given time; and (3) nations and their press systems vacillate continually from one prevailing primary motive in the direction of one or both of the other two. A triangle of motives is employed to illustrate how press dynamism may be conceptualized. Characteristics for press systems driven by each primary motive are cited and illustrated by case summaries. Eight figures are included; 31 references and a table listing characteristics of press systems are attached. (Author/RS)