The chapter provides a comprehensive guide to reliability theory tools designed explicitly for civil engineering structures. It highlights fundamental concepts such as performance functions, reliability indices, and faillure probability, offering a nuanced understanding of structural reliability assessment. Furthermore, it thoroughly explores the sources of uncertainty inherent in soil parameters, elucidating their mathematical modeling techniques and outlining effective procedures for uncertainty identification. Additionally, the chapter provides valuable insights into recommended statistical parameter values drawn from existing literature, thereby equipping engineers and researchers with essential resources for optimizing structural design and performance evaluation in real-world scenarios.