At present, many heterodox economists are concerned with the economics of Michal Kalecki. However, their vision of the historical development of capitalist economies is somewhat different from that of Kalecki himself. This paper makes clear the nature of Kalecki's theory of capitalist development by contrasting his theory with that of the Kaleckians', and considers its significance in the present.While Kalecki viewed capitalist economies as essentially oligopolistic systems, he did not hold that a rise in the degree of monopoly necessarily brought a stagnationist tendency into an economic system. He explained the slowing down in economic growth in the later stages of capitalist development by a semiexogenous factor, namely a decline in the intensity of innovations. Contrastingly, Kaleckians such as Steindl, Baran, Sweezy and Cowling argued that the secular stagnation in capitalist economies is generated endogenously by the concentration and centralization of capital.At present, in studying the process of capitalist development, we have to adopt the view that capitalism changes through the alternation of long-term growth and long-term crisis. In doing so, we should learn from Kalecki's viewpoint that economic growth depends on past economic, social and technological developments.