Over the past 5 years, 7 to 13 percent of receptions in the SPPS were sentenced for a drug offense as the principal offense. An additional 10 to 18 percent were sentenced for other and more serious crimes but their offenses included a drug offense. In 1998, just over 1,200 offenders who entered prison had been sentenced for a main drug offense, and a further 1,600 had a drug offense included in their offenses. Nearly 5,000 drug-misusing offenders were received in prison during 1998. Nearly 80 percent were serving prison sentences longer than 2 months. There were proportionally more severe drug misusers among female prisoners than among male prisoners. The number of prisoners on October 1, 1998, who were classified on entry has having been drug misusers was slightly more than 1,600, 45 percent of the prison population. Cannabis was the most common drug, closely followed by central nervous stimulants, while opiates were involved only to a limited degree. Urinalysis was an important method of maintaining control of the drug situation in prisons. Various measures taken to get prisoners to abstain from drug misuse included personal change programs. On April 1, 1998, just over 2,350 persons under supervision were classified as drug misusers, and a further 2,200 were classified as alcohol misusers. Nearly 1,680 misused both drugs and alcohol. 1 table and 16 figures