Background The suicide rate is higher in prisoners compared with the general population. The aim was to describe the characteristics of and longitudinal trends in prisoner suicides in England and Wales. Method A case series was ascertained from the Safer Custody and Offender Policy Group at the Ministry of Justice and included a 9-year (1999-2007) national census of prisoner suicides. Questionnaires were completed by prison staff on sociodemographic, custodial, clinical and service-level characteristics of the suicides. Results There was a fall in the number of prison suicides and a decline in the proportion of young prisoner (18-20 years) suicides over time. Females were over-represented. Upward trends were found in prisoners with a history of violence and with previous mental health service contact. A downward trend was found in those with a primary psychiatric diagnosis of drug dependence. Drug dependence was found to be significant in explaining suicides within the first week of custody. Conclusions The findings provide an important insight to aid a target set in the National Suicide Prevention Strategy in England to reduce suicides in the prisoner population by 20% and highlight an important area for policy development in mental health services. Examining trends identified subgroups that may require improved mental healthcare and recognized those that appeared to be having their treatment needs more adequately met. Evidence suggests that targeted suicide prevention strategies for subgroups of prisoners are required. © 2011 Cambridge University Press.