Objective: The aim of this study was to determine the knowledge level of secondary school students on hand hygiene and to evaluate " handwashing" behaviors of the students using competency based training approach. Material and Methods: The study group comprised 87 students (6 th, 7th, and 8th graders) of a secondary school in the catchment area of Akpinar Health Care Unit in February 2005. Eighty-four students participated in this intervention study (participation rate= 96.6%). The intervention method was "before-after" training technique. A checklist including 10 steps was used to evaluate the handwashing behaviors of the students. Results: Mean age of the students was 13.46 ± 1.14. Overall, 48.8% were females and 51.2% were males. The knowledge level of the study group was inadequate. For example the answer to the question "How long should one wash his/her hands?", was 20 seconds in 13 students (15.5%), 25 seconds in 20 students (23.8%), and 30-60 seconds in 30 students (35.8%); 21 students (25.0%) replied as "no comment/do not know" to this question. There was an increase in the frequency of "correct" handwashing practices for the 10 steps of the checklist (p< 0.001). Conclusion: Knowledge level of the students about handwashing was inadequate in this study. Conducting training programs at school might be an appropriate approach. "Knowledge" is important to learn behaviors, however, "skill based training methods" are recommended for reflecting "knowledge" to "practice". Copyright © 2006 by Türkiye Klinikleri.