In the thirtieth, the founder of ethology Austrian zoologist Konrad Lorenz put forward the new theory of behavior, which was met with considerable resistance of the dominant views on the mechanisms of behavior, including Pavlov's concept. From his first theoretical works and later on Lorenz debated with Pavlov. However, these debates were not reduced to a disagreement. He appreciated greatly the scientific contribution of Pavlov, and the ideas of the Russian physiologist were often the starting point of his own speculations. His polemics with Pavlov differed very much from his uncompromising controversies with behaviorists. When Lorenz compared Pavlov's views with behaviorism, he often preferred Pavlov's ideas. Lorenz also draw some parallels between the Pavlov's understanding of behavior and the ethological approach. Lorenz's discussion with Pavlov about the nature of conditioned reflex is of particular interest, since it stimulated Lorenz to develop the theory of this phenomenon.