Although the high prevalence of blood-borne viral infections and syphilis in correctional facilities has been well documented globally, such data are sparse from Africa, and there has been no such data from Ghana. This study sought to estimate the prevalence of human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV) and syphilis among prison inmates and officers at prisons in Nsawan and Accra, Ghana. Prisoners and officers in 3 of the 46 prisons in Ghana were surveyed from May 2004 to May 2005. Subjects voluntarily completed a risk-factor questionnaire and provided blood specimens for unlinked anonymous testing for the presence of antibodies to HIV, HCV and Treponema pallidum, the causative agent of syphilis, and the surface antigen of hepatitis B virus (HBsAg). Almost 16 % (3770) of the total of 23 980 prison inmates in Ghana were eligible, and 281 (7·5 %) of those eligible took part, whilst almost 23 % (1120) of the total of 4910 prison officers were eligible, and 82 (7·3 %) of those eligible took part. For the 281 inmates tested, HIV seroprevalence was 19·2 %, 17·4 % had HBsAg, HCV seroprevalence was 19·2 % and reactive syphilis serology was noted in 11 %. For the 82 officers tested, HIV seroprevalence was 8·5 %, 3·7 % had HBsAg, HCV seroprevalence was 23·2 % and reactive syphilis serology was noted in 4·9 %. The data indicate a higher prevalence of HIV and HCV in correctional facilities (both prison inmates and officers) than in the general population in Ghana, suggesting their probable transmission in prisons in Ghana through intravenous drug use, unsafe sexual behaviour and tattooing as pertains to prisons worldwide.