Abstract Recently, a plethora of new and formerly obscure compounds have appeared on the illicit drug market, and many have become quite popular. These new drugs of abuse often prove to be established research chemicals that have diffused out of laboratories and scientific journals and onto the streets. Their rapid appearance and largely unknown character put them into a legal gray area, where they are often referred to by sellers and users as “legal highs,” until emergency scheduling can be invoked. A factor that has contributed to this explosion of new street drugs is the ready access to information about their effects as well as sources of the drugs that has been provided by the Internet. This chapter will survey the types of new designer drugs that are emerging, and provide some basic information about each class. At the end, we provide a commentary about legal issues involved in control of new designer drugs.