Abstract : With the improvement in technology and tightening of performance requirements, the cost and the required precision of assemblies increase as well. There is a strong need for increased attention to tolerance design in order to decrease the uncertainties of tolerancing decisions which can profoundly impact the quality and cost of a gear. Therefore, the objective of this PhD research is the management of geometrical variations and uncertainties focusing on specification models. This research concerning the tolerance analysis was motivated to incorporate and increase the flexibility of the approaches to support different representations of specification models. Also, the uncertainties were reduced by characterizing and proposing specification models. Concerning tolerance analysis, two meshing behavior formulations, two geometrical models (discrete or parametric) and several numerical methods have been proposed and tested. They allow analysis of vectorial tolerance, tolerance by zone, or hybrid formulation, using Monte Carlo Simulation. Concerning the uncertainties, correlation uncertainty formalization has been proposed. It is based on the Axiomatic Design approach, by defining this uncertainty as a confidence interval of the sensibility matrix coefficients. Thus, several specification models have been characterized regarding these uncertainties (correlation uncertainties) and measurement uncertainties to have a global view of uncertainties which affect the conformity decision.