Purpose: This study aims to evaluate the adverse drug effect (ADR) of special vaccines and antimalarial agents, as well as adherence of antimalarial agents, among Taiwanese workers and travelers.Method: A cross-sectional study was conducted among Taiwanese who visited the travel clinic in Mackay Memorial Hospital from 2009 to 2010. Returned postcard was used in the first stage, and phone interview was done in the second stage. Adverse drug effect of the special vaccines (Meningococcal vaccine and Yellow fever vaccine) and antimalarial agents were questioned via both methods and then compared. In addition, adherence of antimalarial agents and the preferred reply method were asked in the interview.Results: The percentage of those with no adverse drug effect was lower among those who returned the postcards than those interviewed by phone (Meningococcal vaccine: 65.2% vs 89.8%; Yellow fever vaccine: 73.4% vs 86.9%; Malaria chemoprophylaxis: 64.2% vs 73.5%, respectively). However, recall bias must be considered due to the later timing of the phone interviews. Adherence rates of malaria chemoprophylaxis were as followed: completed (53.3%); no pills taken (12.3%), incomplete (13.7% stopped in the middle of the trip and 15.7% stopped after returning home). The main reason for incompletion was feeling that malaria chemoprophylaxis was not necessary (male: 36.8%; female: 28.3%).Conclusion: With the rise of international trade and traveling, it is important to build the data of Taiwanese about the ADR after receiving special vaccination and anti-malaria agents. We wished the person who work abroad, short-term stay, or travel, they can initiative to clinic to receive the related chemoprophylaxis, the possibility of infection will be decreased because of workers who did not fear of ADR of chemoprophylaxis.