The average number of persons in custody in Prison Service establishments, including those held in police cells, approximated 49,000 in 1987, about 2,100 higher than 1986 and 5,000 higher than the 1982-1984 period. The population in custody rose rapidly during the first half of 1987, and the prison population at the end of 1987 was about 1,000 higher than 1986. The number of both males and females sentenced to over 18 months rose in 1987. The population of prisoners in police cells, most of whom were not sentenced, fluctuated daily, the average during 1987 being about 540. The average population in Prison Service establishments was 7,400 above the mid-year certified normal accommodation (CNA) in 1987, compared to 5,300 in 1984. The CNA increased by about 1,200 during 1987 to reach 42,550 by the end of the year. The average remand population pending trial or sentence was about 11 percent higher in 1987 than 1986. Between 1986 and 1987, main increases in the prison population were the result of drug offenses and offenses involving violence. Also between 1986 and 1987, the population of adult males serving medium and long-term sentences and the population of young offenders serving sentences of over 18 months increased. As of mid-1987, about 6,700 males and 400 females in Prison Service establishments were from ethnic minority groups, and about 2,350 persons were serving a life sentence. Data are provided on the reconviction of persons released from custody, offenses against prison discipline, and inmate employment. Legislation relevant to the survey and survey procedures are summarized. 111 tables, 7 figures.