A cross-sectional descriptive survey was conducted in eleven sub-districts of Thaibinh City, Viet Nam, to find out the relationship between willingness to pay for counseling-testing service and socioeconomic characteristics of people, and to measure their knowledge about HIV infection and AIDS. The survey was conducted in both of urban and rural area of Thaibinh City, participants aged 19-49 years were randomly selected from the general population to be interviewed. Descriptive analysis and regression analysis were used to describe the association between selected variable as requirement of research objectives. A total of three hundred people were interviewed. The prevalence of knowledge about HIV/AIDS of people was 80.52 ranging from 40% to 100%. People in urban area had higher knowledge about HIV/AIDS, educational level, income and WTP for VCT service. There were differences between male and female in terms of educational level, income and WTP. WTP for VCT servcie ranged from 0 VND to 20,000 VND with the mean was 6,140 VND. Knowledge about HIV was improtant factor affecting willingness to pay for VCT service with positive impact or in other word knowledge about HIV/AIDS could increase WTP for VCT. Educational level was the most important characteristic of individual affecting to knowledge about HIV/AIDS with high wenitivity. There was a disparity between urban and rural area in term of knowledge about HIV/AIDS and WIP for VCT. Individual income also had very important role for improvement the knowledge about HIV/AIDS of people. Willingness to pay for VCT is an important basis to expand VCT service in Thaibinh City. Association between individual socioeconomic characteristics and knowledge about HIV/AIDS may be a basis for implementing intervention programs efficiently according to characteristic of individual.