At the end of the 20th century a variety of data collection were used in social surveys and official statistics. Data could be collected by an interviewer visiting a respondent or phoning a respondent, or through self-administered methods, such as mail questionnaires. Advances in computer technology made computer-assisted survey methods possible, including methods for Internet and web surveys. This variety of data collection methods led to methodological questions, such as, which method to choose? which is best? Recently in survey practice multiple modes of data collection or mixed modes have become more and more popular. In this presentation I will outline the advantages and disadvantages of mixed mode survey designs, starting with an overview of common forms of mixed mode design and discussing reasons for using more than one mode in a survey. This overview will end with a discussion of practical issues and an agenda for future research.