The WM-1 model is the first macromodel of the Polish economy based on monthly data. Most time series are generated by non-stationary processes. Therefore the estimation has been made in such a way that it allows for the cointegration of the variables (ECM, TECM and CVAR models were used). This prevented spurious regressions and ensured appropriate statistical inference. A specification of all the behavioral equations follows economic theory. The model also exploits data from Input-Output tables. In the case of many important equations, the asymmetry of the reactions has been taken into account.