In this work we study the very early phases of the evolution of our Galaxy by means of a chemical evolution model which reproduces most of the observational constraints in the solar vicinity and in the disk. We have restricted our analysis to the solar neighborhood and present the predicted abundances of several elements (C, N, 0, Mg, Si, S, Ca, Fe) over an extended range of metallicities [Fe/H] = −4.0 to 0.0 compared to previous models. We adopted the most recent yield calculations for massive stars taken from different authors (Woosley & Weaver 1995; Thielemann et al. 1996) and compared the results with a very large sample of data, one of the largest ever used to this purpose. We have obtained this by selecting the most rec.ent and higher quality abundance data from a number of sources and renormalizing them to the same solar abundances. These data have been analysed with a new and powerful statistical method which allows us to quantify the observational spread in measured elemental abundances and obtain a more meaningful comparison with the predictions from our chemical evolution model.