Introduction: Previous sentinel surveys of HIV in Nigeria studied pregnant women attending antenatal care, thereby omitting other important high-risk groups. We therefore investigated the prevalence of HIV/AIDS in low-and high-risk populations in the state of Plateau, Nigeria. Methodology: Blood samples were collected by venepuncture from 5,021 adults aged ≥15 years between August and October 2008. At least one major town and one rural community were selected in each Local Government Area (LGA). Samples were initially screened with a rapid HIV testing kit; reactive samples were further tested using Stat Pak. Discordant samples were confirmed using Genie-II. Results: Of 5,021 subjects screened, 245 (4.88%) were seropositive. Local Government prevalence ranged from 0.68% in Bassa to 16.07% in Jos North. On average, LGAs in the Southern Senatorial Zone had higher rates. Most (over 80%) positive cases were younger than 40 years. Females had a significantly higher (6.85%) prevalence than males (2.72%). Age-specific prevalence was higher among females aged 25 to 29 years (2.09%). Risk factors identified for acquisition of HIV infection were previous history of STDs (6, 16.28%); men having sex with men (2, 11.76%); having multiple sexual partners (97; 10.49%); intravenous drug use (10, 7.58%); sharing of sharp objects (20, 4.82%); and history of blood transfusion (21, 3.65%). Conclusion: The seemingly higher prevalence recorded in this survey could be attributed to the inclusion of high-and low-risk groups in the general population, unlike previous reports which studied only antenatal care attendees. This survey provides useful baseline information for further studies.