Sustainable development and the Information Society are two concepts that are not commonly associated. However, both could have a major impact on the other. Information and communication technologies (ICT) may have important negative impacts on the environment. At the same time, ICT can also bring improvements. To provide guidance on how ICT devices and applications can be oriented towards positive effects, new methodology and tools are needed to understand and assess these various effects. In that respect, Life Cycle Assessment (LCA) is a pertinent approach, potentially enabling a holistic and in-depth analysis. This thesis proposes to develop appropriate Life Cycle tools and methodology and to apply them to measure the sustainability of ICT devices and of their applications. Specific objectives are: to explore the possibilities of combining Process LCA (PLCA) and Input-Output LCA (IOLCA), and to develop an operational method for ICT applications; to apply the developed method to assess the direct impacts of a computer network, including software and maintenance and developing strategies, to account for the high renewal rate in ICT technologies; to extend the method to consider not only negative impacts, but also benefits of ICT; to develop a method to address effects on lifestyles and rebound effects, and apply it to assess the impacts and benefits of innovative ICT services; Chapter 1 is a short introduction describing the environmental impacts of ICT and how this work addresses them. Chapter 2 presents the main methodological developments: It looks in detail at how PLCA and IOLCA can be compared and used in a complementary way. A method is developed to compare the two approaches in detail and to evaluate the cut-offs processes – the processes that are not traditionally considered in a PLCA – of two specific ecoinvent processes. The conclusions are that a full integration of PLCA and IOLCA remains difficult with our present level of knowledge. IOLCA could be use to complement PLCA when no other evaluation is available, but IOLCA should also be used as a quality check for PLCA and to determine priorities. Chapter 3 assesses comprehensively the environmental impacts of the computer network of the Ecole Polytechnique Fédérale de Lausanne. The LCA shows that the computers have the highest environmental impact, but also that short-term technology changes can reduce significantly their impact. The use phase dominates the impacts, but the production phase is also significant. Finally, using the Input-Output (IO) approach leads us to the conclusion that the service-linked contribution included in the total cost of ownership - that is, all of the costs associated with the computer network - has a significant impact on the environment. Chapter 4 evaluates the impacts and benefits of the ICT application to help the management of urban networks. The CREM, in Switzerland, uses a telemonitoring system to assess the water, electricity, district heating, and natural gas networks to increase the efficiency of their management. We want to know how the environmental and economical costs of the infrastructure and its maintenance compare with the savings. An LCA has been performed using a tiered hybrid approach. It shows that the savings overcome largely the cost and environmental impacts of the infrastructure. Chapter 5 analyses an innovative service developed by France Telecom. The visiophonic station enables the substitution of physical interviews by virtual interviews. A PLCA of the service shows that the saved km due to the shift from physical to virtual interviews dominates the effects on the environment and that the potential savings are therefore important. However, depending on what is consumed when using the time and financial resources made available by the service, the related impacts counterbalance the savings. Rebound effects must therefore be considered, studied, and addressed in the development as well as the implementation of new ICT services. Chapter 6 concludes with recommendations towards environmental beneficial uses of ICT and identifies what is needed for the necessary further LCA developments.