Background: In South Korea, young adults' smoking prevalence is relatively higher than that of other age groups. Although most hospitality venues are subject to regulations mandating a complete indoor smoking ban pursuant to Article 7 of the Enforcement Rules of the National Health Promotion Act, information is still limited on university students' potential exposure level to secondhand smoke in hospitality venues. This study evaluated indoor secondhand smoke levels at various venues in campus towns. Methods: Using a portable real-time PM 2.5 monitor, we measured indoor PM 2.5 concentration at various venues as an indicator of secondhand smoke exposure. On weekdays, we conducted measurement inside of campus buildings (from 12:00 to 2:00 pm) and in hospitality venues (e.g., PC-rooms, billiard-rooms, and pubs) from 6:00 pm to 8:30 pm. On weekends, we performed the measurement at clubs and bars, which are recognized as trendy venues among young university students. Results: The median of PM 2.5 concentrations was 9.0, 180.4, 41.2, and 44.3 g/m3 in campus buildings, PC-rooms, billiard-rooms, and pubs, respectively. The levels at clubs, nightclubs, and hookah-bars were as high as 982.0, 134.9, and 227.5 g/m3, indicating that PM 2.5 concentrations in these places were 4 to 19 times higher than the 24 hour exposure guideline for outdoor PM 2.5 (50 g/m 3) that will be implemented in South Korea after January 1, 2015. Conclusion: Our study provides evidence for the introduction of more rigorous policy initiatives aimed at encouraging a complete smoking ban in venues, particularly clubs and bars as well as PC-rooms, billiard-rooms and pubs.