Publisher Summary The Internet has radically changed the organization and access to toxicology and other information. The Internet will continue to evolve and the current chapter offers a snapshot of some of the tools now available. Many terms used to describe features of the Internet, such as blog, portal, and discussion forum can be used quite loosely, with standardized definitions hard to come by and sometimes changing over time. The web's future transformation continues to be variously predicted. One model considers the process moving from Web 1.0 (connecting information) to Web 2.0 (connecting people) to Web 3.0 (connecting knowledge) and ultimately to Web 4.0 (connecting intelligence). The challenge for toxicology and the environmental health sciences will be to integrate the ever-expanding data on hazard with exposure, to facilitate better decision making to protect the environment and human health. This chapter presents key characteristics of Internet-based sources of information relevant to toxicology.