This contribution to the 40th Anniversary celebration of the Diffusion of Innovations Theory discusses three health communication projects which applied the tenets of Diffusion of Innovation Theory with differing results: 1. Using voodoo practitioners to pave the way for HIV/AIDS education in Haiti. 2. A food-based approach to improving Vitamin A nutrition in Nepal. 3. Diffusion at the horizon of life: The difficulties of communicating reproductive health to youth in Mali. The article illustrates a spectrum of circumstances in which diffusion theory has been applied, in order to show the application of the theory with different populations or target groups, in different sectors, and in different regions of the world.