Provider-initiated HIV counselling and testing were delivered to inmates on an opt-out basis. All inmates received HIV pretest counselling according to Zambian national and World Health Organization guidelines. Throughout the project, special attention was paid to the vulnerable nature of the inmate population in the context of opt-out testing. Decision to test, testing and post-test counselling were conducted in private, by trained external counsellors who were not affiliated with any prison. Individuals tested positive were referred for HIV care and treatment either at a Ministry of Health clinic or a local nongovernmental organization supporting prison health services.