Under the Misuse of Drugs Act 1971, illegal drugs are placed into one of 3 classes - A, B or C. This is broadly based on the harms they cause either to the user or to society when they are misused.
The class into which a drug is placed affects the maximum penalty for an offence involving the drug.
For example, Class A drugs attract the most severe penalty as they are considered likely to cause the most serious harm.
Drugs controlled under the Misuse of Drugs Act are illegal to have, produce, give away or sell.
And recently new 'legal highs' have been developed to mimic the effects of illegal drugs like cocaine and ecstasy but are structurally different enough to avoid being classified as illegal substances under the Misuse of Drugs Act. However, they can still have dangerous side effects.
Some drugs do have a legitimate use, as a medicine, in research or in industry. To use, import or produce these drugs you need to obtain a licence from the Home Office.