Performance enhancing drugs are any substances taken to increase a particular skill-set. Most often the term is used in reference to steroid use by professional athletes. Other substances may also be taken to improve performance, including human growth hormones.

The use of enhancement substances for sporting events dates back at least to ancient Greece, where writings refer to 'performance potions' and 'performance elixirs' given to athletes in preparation for major games. It was not until the latter part of the 20th century that testing technology became sufficiently advanced to begin screening athletes regularly and enforcing bans on the use of steroids and other enhancements.

Most performance enhancing drugs are taken orally as pills, though some may be injected intravenously, or taken in powder form mixed in with health shakes. The number of designer steroids being produced each year increases at a staggering rate, making it a difficult job for athletic organizations to track each one on their ban lists, and test for them accordingly.

Performance enhancing drugs may be used for a number of reasons, including dulling the pain response in the body, building muscle at an accelerated rate, reducing weight, lowering stress, and even hiding other drugs that may be in the system. Different drugs are used for each of these purposes, with some athletes taking a daily 'cocktail' which consists of a variety of steroids and growth supplements.

The most popular performance enhancing drugs for building muscle mass are anabolic steroids, a synthesized hormone that increase a number of physiological functions--including appetite, bone growth, and protein synthesis--which aid in the rapid development of muscle tissue. Anabolic steroids have a number of drastic side-effects, including a lowering of the voice, higher levels of hair growth, and the shrinking of testicles in men.

Severe diuretics, (which increase the frequency of urination), are also used illicitly in many sports to artificially speed the loss of weight. This can have consequences which include lightheadedness and even fainting spells. The use of intense diuretics is particularly troubling because the users are often young children in sports such as gymnastics where weight can be a critical factor.

Recently, the use of pharmaceutical enhancement drugs in the musical world has begun receiving some attention. The problem of heavy stress affecting performance (commonly known as stage fright) is one which plagues performers of all levels. The use of a synthetic, Inderal, has sparked controversy as to the ethical considerations in using an enhancement drug before performing musical pieces.

As technologies continue developing, the job of determining whether an athlete has taken performance enhancing drugs becomes more and more difficult. In 1999, the foundation of the World Anti-Doping Agency provided a strong start to better coordinating drug testing and punishment throughout the international sports community. With funding from nations around the world, as well as the International Olympic Committee, the WADA has developed strong standards and a research branch charged with tracking new drugs and developing tests before they reach widespread use.