The cross-sectional descriptive study was conducted at 15 communes of 5 provinces including Ha Tinh, Thanh Hoa, Ha Nam, Ha Tay and Hai Phong. The study subjects were 390 mother having children under 5 years old. The purpose of the study is to identify the behavior on handwashing with soap of the study subjects. Results show that: the rates of respondents washing their hands with soap before feeding children and after urinating were 36.2 percent, 18.1 percent respectively. The rate of the mothers washing their hands after defecating, after cleaning the children's buttock and the chamber-pot were 68.4 percent, 66.8 percent and 74.0 percent respectively. Among these mothers, the proportion using the soap for handwashing ranged from 84.1 percent to 97.1 percent.