André-Nicolas Chené (National Research Council of Canada) Title: Determining the fundamental parameters of Wolf-Rayet stars. Abstract: Wolf-Rayet (WR) stars have typical wind densities which are an order of magnitude higher than those of massive O stars. In spite of their rarity, they contribute large amounts of energy, momentum and matter to the ecology of their host galaxies, making them crucial constituents of the universe. Also, they are the prime candidates for the immediate progenitors of long-soft gamma-ray bursters (GRBs), and they provide a signature of high-mass star formation in galaxies. Here, I will present how long term monitoring and surveys can be used to determined the poorly known fundamental parameters of WR stars.