The work presented here look into the early stages of pedogenesis of constructed soil. Indeed human activities (e.g. agriculture, industry or urbanism) induce soil degradation but also creation of new soil with pedological, geological or man-made materials. Moreover, the coverage of the “newly called” Technosols (Rossiter, 2004; Lehmann & Spaargaren, 2005) continuously increases. However, the genesis of those soils, developed on non traditional substrates and largely due to intensive human activity, is poorly studied. In the context of the development of an innovative process of reclamation of degraded sites, three constructed soils are studied. They are made of histi-technic materials (compost and paper sludge) and of one spoli-technic material (thermally treated industrial soil). These materials are associated in a pilot-scale set-up of in situ lysimetric plots (10 x 10 m). Thus, our objectives are to monitor the early pedogenic evolution by: i) evaluating and measuring the reactivity of the constructed soils under natural environmental conditions; ii) describing the evolution of the structure in these soils from the scale of aggregates to the whole soil profile. The methodology is based on a field approach and an adaptation of the classical pedological tools of description. A balance of the plant-water-soil system is realised on the plots by measuring, collecting and analysing the rainwater, the leachates, the plants and the soils for their major and trace element contents. Moreover, pedological pits are periodically dug to realise an exhaustive description of the parameters of the soil profiles. Due to the properties of the components of the constructed soils (especially paper sludge) the first pedogenic process observed is a limited but continuous decarbonatation. Results also illustrate the development of sub-horizons inside the soil profiles and a global compaction of all the soils. Finally, a precise description of the evolution of the aggregation mechanisms is realised thanks to particle size and density analysis. Major evidences that constructed soils go through early pedogenic evolution processes are highlighted with this work. Furthermore, an analogy can be done between Technosols and natural soils. Indeed, this study indicates for example, that similar mechanisms and processes occur in Rendzic Leptosol and constructed soils. Acknowledgements: This project is supported by the GISFI program and was founded by the Etat Français (ANRT), Région Lorraine (CPER), ADEME, EPFL and Bail Industrie. Rossiter D.G., 2004, Proposal: Classification of urban and industrial soils in the World Reference base for Soil Resources (WRB) 2006, DRAFT for comments Lehmann A., Spaargaren O., 2005, Technosols as a proposed soil group for the WRB, SUITMA 2005 Proceedings