Background: The prevalence of HIV in specific areas of South Africa and its impact on haematological parameters are largely unknown. Objectives: To (1) describe the prevalence of HIV, (2) stage HIV based on CD4 counts, and (3) determine haematological parameters amongst participants in Mangaung, Free State Province. Method: Blood specimens were obtained from 419 participants in formal and informal settlements in Mangaung. Participants were 25–64 years of age; 23.4% were male. Males and females were a mean of 45.1 and 44.3 years of age, respectively. Screening for HIV status was performed. Positive results were confirmed by a second test. Full blood counts were performed on all participants, and CD4 counts only on HIV-positive serum. Results: The overall prevalence of HIV was 40.8%. The highest prevalence occurred in the 31–40 years age group, with 38.4% of females and 39.5% of males being infected. More than 33% of HIV-uninfected participants were 51–60 years of age. No significant change in CD4 count with age was observed, probably because 19.1% of the 225 respondents who reported using medication were receiving antiretroviral (ARV) treatment. Haematological results showed that HIV-infected participants had significantly reduced values for haemoglobin, leukocytes, neutrophils and lymphocytes, compared to HIV-uninfected participants. The mean corpuscular volume (MCV) was significantly higher in HIV-infected participants. Conclusions: A high prevalence of HIV-infection was found. Anaemia and significantly reduced white blood cell counts were observed in the HIV-infected group. No significant change in CD4 counts with age was observed and could possibly be attributed to ARV therapy.