The statistics relate to drugs controlled under the Misuse of Drugs Act of 1971, which came into force on July 1, 1973. The act divides drugs into three categories according to their harmfulness. Class A drugs include cocaine, dextromoramide, dipipanone, heroin, LSD, methadone, morphine, opium, and pethidine. Class B drugs include amphetamines, barbiturates, cannabis, and methaqualone. Class C includes all other drugs. Statistics on drug seizures cover seizures made by police and officials of customs, excise, and other bodies such as the Port of London Authority. Seizures by customs and excise officials account for about 1/7 of the total number of seizures but for most of the quantities seized. Seizures involving more than one drug are counted as a single seizure in the total number of seizures, but are counted separately against each individual drug or drug class involved. Each customs case is counted as a single seizure even where it includes seizures made on a number of separate occasions. Offenders with more than one offense are counted as a single offender in the total number of offenders, but are counted once for each separate offense type. Data are presented for immediate custody sentences, including unsuspended imprisonment, partially suspended sentences, and youth sentences. Youth sentences comprise youth custody, detention centers, borstal training, training school orders, and young offender institutes. 38 tables