In the article, the nature of morphological productivity as a property of a morphological process to give rise to new derivational formations is discussed. The authoress introduces the question whether productivity is a qualitative or a quantitative notion and how it can be measured. In the next sections she presents not only theoretical statements given in Polish literature but also findings of various computational and generative works concerning productivity and its restrictions. The presentation is enriched with a description of the results of three tests of productivity on Polish empirical data.