The purpose of this paper is to introduce the geotechnical engineering community to the treatment of uncertainties in site characterization within the framework of the second-generation Eurocodes. To do so, the main uncertainties related to the Ground Model, the ground properties and the groundwater levels are described before discussion of the statistical and modelling involved. This paper also explains the determination of “representative values” of ground properties within the framework of the Second-Generation Eurocode 7, either selecting the value based on engineering judgment and comparable experience, being in this case termed a “nominal value”; or evaluating the value by statistical methods, being in this case termed a “characteristic value”. Additionally, since 2nd -Gen Eurocode 7 allows using reliability-based methods for the verification of limit states, the paper gives some guidance for choosing probability distribution types, and for assessment their parameters like the mean and standard deviation. Finally, two examples are provided to show how to deal with the new elements involved with uncertainty treatment in terms of statistical analysis and probabilistic modelling.