Scientific surveys are an essential tool in empirical social research. They influence public opinion and decisions in many areas of the economy and society. As indispensable as surveys are, they are also prone to errors—due to the nature of the questions or unusual responses. The book discusses the current development from telephone to internet as a survey medium. Using a large-scale access panel, which consists of pools of individuals willing to participate in surveys, it introduces the design, methods, potential sources of error, and result evaluation in the conduct of surveys.