This project was designed to evaluate different criteria used in the interpretation of the human immunodeficiency virus type 1 (HIV-1) Western blot assay on a group of serum samples blinded to the examiner that were collected from individuals attending three different public health departments in central North Carolina. Each individual also completed an anonymous linked questionnaire regarding sociodemographics and risk factors for blood-borne infections. All of the Western blot assays for human immunodeficiency virus type 1 were interpreted according to the criteria established at the University of North Carolina Hospitals, Chapel Hill, the Centers for Disease Control, Atlanta, Ga, in association with the Association of State, Territorial, and Public Health Laboratory Directors, Iowa City, Iowa, the American Red Cross, Washington, DC, the Consortium for Retrovirus Serology Standardization, Davis, Calif, and the Food and Drug Administration, Washington, DC. The results obtained were grouped as positive, negative, and indeterminate according to each organization's criteria and analyzed in the context of the associated risk factors. The results indicate that institutions performing human immunodeficiency virus type 1 Western blot confirmatory testing should adopt the criteria of the Centers for Disease Control and the State, Territorial, and Public Health Laboratory Directors.