Handwashing is a well known practice to prevent the hospital-acquired infections, and it is also a basic procedure of the nosocomial infection control programs. This research is conducted to use PRECEDE model to investigate the factors affecting nurses¡¦ performance in handwashing practices. We conducted a cross-sectional study to investigate 212 nurses working patients` heaithcare from a medical center of north Taiwan, and a quota sampling method was used to analyze nurses¡¦ handwashing practices. The results of this research includes (1) the major causes affect nursing staffs¡¦ performance in handwashing practices include attitudes (enthusiastic and passive), encouragements from colleagues, and feedback of the nosocomial infection rate or density. (2) different perfessional department and different ward type also affect the performance of nurses¡¦ handwashing practices. (3) nurses washed their hands often after contacting patients¡¦ body substances, and they usually forget to wash their hands after checking patients¡¦ medicine charts. (4) seif-reported factors for poor adherence with handwashing are heavy work loading and taking patients¡¦ needs priority. The suggestions of this research are (1) providing nurses the routine feedback information regarding the changes in nosocomial infection rate versus their performance in handwashing practices. (2) making nursing supervisors and their colleagues to understand the importance of handwashing practice as well as encouragement, reminding, and supporting. (3) the above two suggestions should be executed continually. From the positive feedback, it shall enhance nursing staffs` attitudes to improve their handwashing practices, and then, nursing staffs will be willing to keep excellent performance in handwashing practices.