In fall 1995, the worldwide-accessible Web Experimental Psychology Lab (http://www.genpsylab.unizh.ch) opened its doors to Web surfers and Web experimenters. It offers a frequently visited place at which to conduct true experiments over the Internet. Data from 5 years of laboratory running time are presented, along with recommendations for setting up and maintaining a virtual laboratory, including sections on the history of the Web laboratory and of Web experimenting, the laboratory's structure and design, visitor demographics, the Kids' Experimental Psychology Lab, access statistics, administration, software and hardware, marketing, other Web laboratories, data security, and data quality. It is concluded that experimental data collection via the Internet has proven to be an enrichment to science. Consequently, the Web Experimental Psychology Lab will continue and extend its services to the scientific community.