Fiscal policy was key determinant of macroeconomic behavior during the 80s, however it is necessary to distinguish the effects of shocks over fiscal policy from those resulting of policy decisions. For that purpose the study uses, with an adjustment, the methodology developed by Marshall and Schmidt-Hebbel (1989) that decomposes the deficit by its causes which are then analyzed from the point of view of their determinants. The study is complemented with the impacts of those determinants in a more general framework with a CGE model. The analysis was implemented for two periods, the first of crisis 1980-1984 and the second of stabilization 1985-1987