Avionics Division of Saab AB develops advanced electronics that need to be robust and work in harsh environments with for example extreme temperatures and cosmic radiation without any failure. To succeed with this the electronics need to be simulated and tested. Therefore this thesis work is done to strengthen the Avionics Division’s knowledge of hardware modelling and simulation by evaluating the simulation tools LTSpice, PSpice and SystemVision, their functions and capabilities. In this thesis a survey is carried out with help of a questionnaire to study the Avionics Division’s needs for simulation. The survey is underlying an analysis of the analyses that can be performed by the simulation tools for example Sensitivity analysis, Worst Case analysis, Monte Carlo analysis and Parametric Sweep analysis. The different analyses are discussed in the thesis. The questionnaire is also underlying an analysis of the tools LTSpice, PSpice and SystemVision. The result of the analysis is summarized in Table 1. A case study of a circuit simulation in SystemVision, based on an existing circuit used by Avionics Division, is also done within this thesis work. The study is done to evaluate the tool’s usability, to see if it is easy to perform a simulation and if it is easy to find and use suitable models from the model library. The case study describes how a simulation is performed in SystemVision and how an AC analysis of a Butterworth filter is done. A stability and reliability check of the tool is performed as well as a robustness simulation. The analyses were easy to do and the overall impression is that SystemVision is reliable and user friendly structured. In order to check and compare the results of the AC analysis the same analysis is performed using LTSpice. The comparison shows that the results differ. This depending on that the models of the circuit were some what different in LTSpice and SystemVision. The final conclusion is that SystemVision would fit within Avionics Division’s workflow. Using SystemVision demands education of the engineers to secure maximum use of all the advantages of SystemVision.