Two-step flow model was propouded by Paul Lazarsfeld and Elihu Katz. Unlike the hypodermic needle model which considers mass media effects to be direct, the two-step flow model stresses human agency.

According to Lazarsfeld and Katz, mass media information is channeled to the "massess" through opinion leadership. The people with most access to media, and having a more literate understanding of media content, explain and diffuse the content to others.

Two-step flow model laid the foundation for diffusion of innovations.