Differences between traditional laboratory research and Internet-based research require a review of basic issues of research methodology. These differences have implications for research ethics (e.g., absence of researcher, potential exposure of confidential data and/or identity to a third party, guaranteed debriefing) and security (e.g., confidentiality and anonymity, security of data transmission, security of data storage, and tracking participants over time). We also review basic design issues a researcher should consider before implementing an Internet study, including the problem of participant self-selection and loss of experimental control on the Internet laboratory. An additional challenge for Internet-based research is the increased opportunity for participant misbehavior, intentional or otherwise. We discuss methods to detect and minimize these threats to the validity of Internet-based research.