Marijuana is the most commonly used illicit drug in America today. The term marijuana, as commonly used, refers to the leaves and flowering tops of the cannabis plant.

A tobacco-like substance produced by drying the leaves and flowering tops of the cannabis plant, marijuana varies significantly in its potency, depending on the source and selection of plant materials used. The form of marijuana known as sinsemilla (Spanish, sin semilla: without seed), derived from the unpollinated female cannabis plant, is preferred for its high THC content.

Marijuana is usually smoked in the form of loosely rolled cigarettes called joints or hollowed out commercial cigars called blunts. Joints and blunts may be laced with a number of adulterants including phencyclidine (PCP), substantially altering the effects and toxicity of these products. Street names for marijuana include pot, grass, weed, Mary Jane, Acapulco Gold, and reefer.

Although marijuana grown in the United States was once considered inferior because of a low concentration of THC, advancements in plant selection and cultivation have resulted in highly potent domestic marijuana. In 1974, the average THC content of illicit marijuana was less than one percent; in early 1994, potency averaged 5 percent. The THC of today's sinsemilla ranges up to 17 percent.

Amphetamine, dextroamphetamine, and methamphetamine are collectively referred to as amphetamines. Their chemical properties and actions are so similar that even experienced users have difficulty knowing which drug they have taken.

Amphetamine was first marketed in the 1930s as Benzedrine in an over-the-counter inhaler to treat nasal congestion. By 1937, amphetamine was available by prescription in tablet form and was used in the treatment of the sleeping disorder narcolepsy and the behavioral syndrome called minimal brain dysfunction (MBD), which today is called attention deficit hyperactivity disorder (ADHD). During World War II, amphetamine was widely used to keep the fighting men going; both dextroamphetamine (Dexedrine) and methamphetamine (Methedrine) became readily available.

As use of amphetamines spread, so did their abuse. Amphetamines became a cure-all for helping truckers to complete their long routes without falling asleep, for weight control, for helping athletes to perform better and train longer, and for treating mild depression. Intravenous amphetamine abuse spread among a subculture known as "speed freaks." With experience, it became evident that the dangers of abuse of these drugs outweighed most of their therapeutic uses.

Increased control measures were initiated in 1965 with amendments to the federal food and drug laws to curb the black market in amphetamines. Many pharmaceutical amphetamine products were removed from the market and doctors prescribed those that remained less freely. In order to meet the ever-increasing black market demand for amphetamines, clandestine laboratory production mushroomed, especially methamphetamine laboratories on the West Coast. Today, most amphetamines distributed to the black market are produced in clandestine laboratories.

Amphetamines are generally taken orally or injected. However, the addition of "ice," the slang name for crystallized methamphetamine hydrochloride, has promoted smoking as another mode of administration. Just as "crack" is smokable cocaine, "ice" is smokeable methamphetamine. Both drugs are highly addictive and toxic.