For most applications trying to interpret the real world uncertainties will be an important factor to consider, which is also true for Life-Cycle Assessment used for estimating total environmental impact during the life-cycle of products, services, buildings, structures, roads etc. The construction and usage of infrastructure are major causes of emissions and energy use, thus making it even more important for society to aim at reducing this impact. One way of reducing environmental impact is by using LCA to show improvements for specific items and/or benefits of using a specific solution over another. To be able to use LCA, or any other calculated estimation, for comparisons it is of great importance to incorporate effects of uncertainties and to understand where such uncertainties have their sources. Otherwise, any attempt on comparing two solutions will be flawed and there is a risk for bias towards a specific solution. The aim of the work presented in this report have been to describe and discuss the types of uncertainties present in a LCA, and to discuss their importance, source and influence. An extensive review of the current state of the art of both uncertainties in general and specifically for LCA have been performed to find the most common ways of including uncertainties in LCA, with focus on the possibilities and limitations of different types of methods. It was found that many previous attempts on including uncertainties in LCA exists, and they showed that it is now possible to using probabilistic methods such as Monte Carlo simulations to incorporate uncertainties in LCA-tools, since the computational capacity have increased. The common problem for all previous studies and the study presented here is the availability of validated input data including uncertainty estimations. Initiatives exist for data quality control; however, they do not fully consider the effect of uncertainties, and typically have been limited to the consideration of variations in emission factors only. Other factors such as system boundaries and choices made by the user have a much larger influence on the result than a small variation in the emission factor itself. To evaluate this, the basis for a methodology considering uncertainties in LCA and possibilities for controlling these uncertainties is presented. The methodology is based on general definitions of uncertainties to be able to understand the source and characteristics of each affecting parameter and for making informed decisions on how to reduce the uncertainty depending on the purpose of the LCA. This kind of methodology will especially be valuable for raising awareness of uncertainties in LCA for different stages of the building process. The possibility of including uncertainties in a LCA-tool for infrastructures in also presented, showing possibilities for studying the sensitivity of the input parameters and the propagation of uncertainties. A case study is used to demonstrate these possibilities, showing the importance of considering uncertainties in all input parameters. It is shown that the influence of other factors apart from the emission factors can be large, such as material amounts and expected service life, and that they have to be considered if reasonable results are sought. It should be noted, however, that the case study presented in this report serves illustrative purposes and includes significant simplifications.