In Concurrent engineering, design solutions are not only produced by individuals specialized in a given field. Due to the team nature of the design activity, solutions are negotiated. Our objective is to analyse the argumentation processes leading to these negotiated solutions. These processes take place in the meetings which group together specialists with a co-design aim. We conducted cognitive ergonomics research work during the definition phase of an aeronautical design project in which the participants work in Concurrent Engineering. We recorded, retranscribed and analysed 7 multi-speciality meetings. These meetings were organised, as needed, to assess the integration of the solutions of each speciality into a global solution. We found that there are three main design proposal assessment modes which can be combined in these meetings: (a) analytical assessment mode, (b) comparative assessment mode (c) analogical assessment mode. Within these assessment modes, different types of ar...