A pattern and frequency of the inappropriate use of certain drugs eventually culminates in their classification as drugs of abuse or addiction. The classes of drugs of addiction include stimulants, central nervous system (CNS) depressants and sedatives, opiates, hallucinogens and inhalants. Amphetamines, methamphetamines, MDMA and cocaine are some of the drugs well recognized for their stimulating effects. Alcohol continues to be the main drug of abuse among CNS depressant drugs, and several licit drugs among the benzodiazepines, barbiturates and sedative hypnotics, obtained by overprescription are also found among the CNS drugs of abuse. Among the opiates, traditional drugs, such as morphine and heroin, are still popular among drug users. However, the ease of acquisition due to trafficking and overprescription of hydrocodone, oxycodone, methadone and propoxyphene has given popularity to these drugs among the opiates. Of all drugs considered, marijuana is probably a close second to alcohol in frequency and popularity among drug abusers. Inhalants are popular amongst youths, but are also abused by adults and homosexuals for their potential to enhance sexual enjoyment. The use of these drugs varies from location to location. While use of some of the drugs cuts across both occupational and socioeconomic groups, others are used predominantly within certain occupational groups. The driving force behind any future classification of a drug as a drug of addiction will be determined, not so much by its intended use, but by the drug user. Additionally, the availability of a drug and its regulation, or absence of regulation, will likely contribute to its abuse potential. The longer it takes for the recognition of the abuse potential of a drug, the greater the probability that the drug will acquire a classification as an abused drug. What follows the identification and classification of a drug as being a drug of addiction is a swath of adverse effects due to abuse, and which cut across the social, economic and political profile of society at a staggering cost, measurable eventually in terms of the level and extent of human suffering.