This paper studies the dynamic and stochastic properties of fixed investments (IL) for five Italian sectors and for the period 1930-1991. Moreover, it analyses the relationship between the trend and cyclical innovations of IL and between these two types of innovations with those of GDP, real money balances and the real interest rate. We find that the five sectors share four common trends, but only one common cycle. As for innovations, trend and cyclical innovations are in general negatively correlated with the single exception of GDP. Trend innovations are generally more important than cyclical innovations, but in the case of real money balances the opposite is true. Finally, we only find a statistically significant correlation between investment trend innovations and GDP trend innovations: a result which offers strong support in favor of the accelerative hypothesis, i.e. one of the most popular models in the study of investment decisions.