This study aimed to identify and compare psychosocial and behavioral factors associated to STD/AIDS risk among students enrolled in the first and last years of the Nursing and Medical Undergraduate Programs at State University of Londrina. A convenience sample was selected from 263 enrolled students, and the 183 students who were sexually active (70.4%) had their data assessed. The Aids Risk Reduction Model framework was used to design the questionnaire in which a 5% statistical significance level was considered. Some risk factors were identified such as the perception of invulnerability, multiple sexual partners, consumption of alcoholic beverages before intercourse, and the discontinuous use or no use of condom. The risk factors are common both to the freshman and senior students, with no significant differences related to the passage of time or to the students' higher educational level. Senior students tend to be monogamous which makes them feel safer and decrease the use of condom with their sexual partners.