This study evaluates the prevalence of HIV stigma in Spain and analyzes some variables that may affect its existence. In 2008, we conducted a computer-assisted telephone survey of 1607 people, representative of the Spanish population. Two-wave random stratified sampling was performed, first selecting the home and then the person, depending on the rates of age and sex. About 50% of the population feels discomfort about potential contact with people with HIV and tries to avoid it and 20% advocate discriminatory policies involving physical or social segregation of people with HIV. The belief that HIV is easily transmitted through social contact (15%) and blaming people with HIV for their disease (19.3%) are associated with stigmatization. Degree of proximity to people with HIV, political ideology, educational level, and age are also associated with the degree of stigmatization. According to these results, we suggest that, in order to reduce stigma, we need to modify the erroneous beliefs about the transmission pathways, decrease attributions of blame to people with HIV, and increase contact with them. These interventions should particularly target older people, people with a low educational level, and people with a more conservative political ideology.