The first part of the paper deals with the effects of an exogenous variation in the monetary interest rate on the real equilibrium position of the economic system in a Kaleckian effective demand model. Different regimes of accumulation are derived and it is shown that a negative relation between the interest rate and the equilibrium rates of capacity utilization, accumulation and profit usually expected in post-Keynesian theory only exists under special conditions. In the second part the model is applied to the data of some major OECD countries, the relevant coefficients are estimated and the relevance for an explanation of the course of GDP and capital stock growth since the early 1960s is discussed.