Quantitative data on various indexes of national development--mass media, "horizontal communication" (mail, telephones, and telegrams), democracy, social growth, literacy, and urbanization--were collected and estimated for more than 100 developing countries for roughly the decade between 1970 and 1980. These data were then used to test various theories and definitions of communication development. The analyses revealed that in all geographic regions, broadcasting showed spectacular growth, while print media grew only modestly. Horizontal communication, social growth, literacy, and urbanization showed some growth, while democracy--defined in Western terms as civil and political liberties--did not fare well in the Third World. Causal inference analysis of the data showed little support either for the original dominant paradigm of communication development that mass media could spur economic and political development or for alternative theories that emphasize horizontal communication and social development. (Author/HOD)