A new phenomenon in the drug market has appeared in recent years: there has been an increase in the number and types of designer drugs. A massive influx of these structural and/or functional analogs of controlled substances has resulted in an increase in their marketing and abuse. At present, these drugs are significantly more widely available compared to previous years because they are relatively inexpensive and marketed as being safer than classic drugs of abuse. The most important factor in the spread of designer drugs is that the majority of these substances are undetectable as drugs or illegal drugs in standard drug testing procedures. The biological effects of these substances are largely unknown to both users and medical scientists. However, most known cases of abuse have shown serious and dangerous physical and psychological reactions in users. The manufacturing and marketing of designer drugs presents a major challenge for specialist sectors, especially laboratories that have to test these substances. This highlights the important role of drugcontrol institutions and regulatory and legislative bodies to determine the legal status of these drugs, which are designed and marketed - mostly through the internet - as being legal. All of these factors make it incumbent upon these sectors to form a unified goal and strategy to control these substances and prevent their spread. This review provides fundamental information about designer drugs. This will provide an accurate overview of their status, and will aid future work to develop a regulatory and legislative strategy to combat their manufacture, marketing, and use.