Objective: to improve knowledge of health staff regarding Sexually transmitted infections (STI). Method: a pre and post-intervention study was carried out among 159 health staff working in 16 communes of Ba Vi district, Hanoi. Descriptive methods and Cochran test were used to compare the results before and after intervention. Results: The intervention improved significantly basic knowledge of health staff as compared to pre-intervention (p0.05) in almost all aspect of STI. For many answers, that were not correct before intervention, had been increased significantly after intervention (p0.05), especially risk factors, transmission routes and partner notification of STI. However, before intervention, health staff had high percentages (90 percent) of correct answers about gonorrhea, syphilis, and those were not much significantly improved after intervention. Conclusion: repeated intervention significantly improved knowledge of health staff about STI.