There are well known correlations between galaxy properties and environment, from rich clusters to low density regions. Are these correlations established during galaxy formation, or are they the end product of a density-driven evolution? I tried to answer to this (still open) question using the VIMOS-VLT Deep Survey data sample, that allowed me to study galaxy environment homogeneously up to z=1.5. I focused my attention on both the computation of the 3D density contrast field and the production of a robust group catalogue. In this talk I will present my PhD work: the algorithms used to compute the density contrast and to identify groups, the main results on the study of the colour-density relation, as a function of redshift and luminosity, and the group catalogue characteristics.