Early diagnosis of HIV improves the effectiveness of treatments and stops the progression of the disease. The influence of personality and other psychological variables in testing for HIV is analyzed. The first part of the study is composed of 4,929 young people (M age = 20.45, SD = 2.16). For the second part, young heterosexuals who participated in a broader project on HIV prevention were selected (n = 240, M age = 20.78, SD = 2.29). Only 23.3 % of the total sample have ever been tested for HIV antibodies. The main reason for not testing was fear of positive result (25.4 %). Statistically significant differences in Agreeableness (p = .027), Trust (p = .022) and Straightforwardness (p = .024) were found between HIV-tested and not HIV-tested youth. Trust explained 3.3 % of variance of HIV-test. Knowing barriers to testing and individual differences could be useful in developing preventive campaigns.