Genetic Algorithms (GAs) are search algorithms that imitate nature based on Darwinian survival of the fittest approach. They are well suited for searching among a large number of possibilities for solutions because they exploit knowledge contained in a population of initial solutions to generate new and potentially better solutions. GAs have several advantages over conventional search techniques Application of GA's methods in Civil Engineering field have been developed in recent years such as in construction management for optimizing the cost or working time. This method is also used in structural engineering for optimization of structural elements cross section and their weight, in topology optimization and geometrical specification of structural elements. This book introduces the basics and principlas of GA and explain it’s applications in designing and optimizing of structures.