The manufacture and use of products are human activities that are based on a certain consumption of energy and materials and as such, significantly affect the quality of the environment and life on Earth. The current rate of industrial development, the growth of the population and the desire for a better quality of life of the population have a negative impact on the environment, which is becoming more pronounced every day. The impacts of products, i.e. materials, on the environment are often studied today using a methodology such as the Life-cycle analysis technique (LCA). The LCA method examines the entire life cycle of a product (from the production of raw materials to disposal or recycling at the end of the product's life) and assesses its impact on the environment. However, LCA is exclusively a tool for the evaluation and mutual comparison of alread y existing products and cannot be considered as a tool for the ecological design of a new product. It is considered that about 80% of the "burden" for the environment, from the future product, occurs in the early design phase while many decisions can still be changed. Based on the need to take environmental impact into account at the early stages of design, an eco-audit tool was developed. The tool for eco-auditing, which is the central point of this final work, is embodied in the program package "CES EduPack". The mentioned tool provides an insight into all phases of the product's life cycle in terms of energy consumption and CO 2 emissions, but also guides the designer in the search for more suitable options during the eco-design process. In this fina l paper, an ecologically sustainable approach to the methodical construction of the load -bearing structure of the car trailer is presented. The paper presents the process of designing, i.e. making variants of the load-bearing structure of the car trailer, using a methodical approach. After that, the constructive development of the load-bearing structure of the car trailer was carried out. By applying CAD programs, the "embodiment" of the product and the control of stress and deformation of the structure are shown. The eco-audit tool, implemented in the "CES EduPack" software package, was used to perform an eco -audit of the structure. A review of the entire ecoaudit methodology was also made and conclusions were presented.