The book "Uncertainty Assessment of Large Finite Element Systems" offers a comprehensive analysis of uncertainties in engineering mechanics, particularly in relation to the analysis of large finite element systems. In recent years, the synchronization between stochastic and deterministic computational techniques has proven crucial for addressing challenges in modern structural mechanics. This monograph presents novel methods for uncertainty assessment based on the Karhunen-Loève expansion. These methods are formulated for both scalar and vector stochastic processes as well as for random fields. Especially for highly nonlinear structures, direct Monte Carlo simulation has proven to be an advantageous solution method. The developed procedures are illustrated through practical applications, providing readers with valuable insights into the application of these techniques in practice.