The aim of this paper is to study the mechanisms through which aggregate demand and income distribution affect the rate of growth, in a post-keynesian framework rooted in the works of Michal Kalecki. Thus, this paper addresses some issues that are put aside by neoclassical theory, which focuses on supply side phenomena to explain growth. The Say’s law refusal implied by the framework employed allows to determine the influence that demand exerts on economic growth, which also depends upon the sensibility of saving and investment decisions to changes in the income shares of workers and capitalists.