This case study focuses on the etiology and epidemiology of four sexually transmitted infections (STIs):  human immunodeficiency virus (HIV), hepatitis B, chlamydia, and gonorrhea. The case provides background information about each disease and three classroom activities: a doctor-patient role play, an interactive game, and a concluding activity for small groups. The role play teaches students about symptoms, social relevance, and importance of safe sex practices and regular STI testing. The interactive game, described in the teaching notes, places students in the role of travelers to three different countries. The concluding activity gives students an opportunity to work collaboratively to complete a set of questions and a summary chart (see teaching notes). Overall, the case study provides insight to students about the causes, modes of transmission, and importance of preventing the spread of STIs. The case is appropriate for use in courses that cover human biology, microbiology, infectious disease, public health, or HIV education, and is ideally suited for high school upperclassmen and college freshmen.