Abstract: Objective To understand the situation and influencing factors of sexual behaviors among male construction workers in Shanghai and to supply the evidence for implementing AIDS/sexually transmitted disease(STD) prevention and intervention effectively.Methods A face-to-face questionnaire survey was conducted among 1757 construction workers randomly selected from 18 sites in three districts of Shanghai.The information collected included demography, age at first sexual behavior, premarital and extram a rital sexual activity, commercial sex, and sex violence.Mean while, the construction workers from six sites were followed up for a half of year in order to observe the change of their high risk sexual behaviors.Results Most of construction workers were young/middle aged with an average age of 39±10.6 years and with low education.Among them, 21.6% had at least 2 sexual partners and 7.3% ever had commercial sexual behavior.Among the married workers, the proportions of premarital and extramarital sexual behavior were 31.2% and 10.1%, respectively.The influencing factors of high risk sexual behaviors included age, gende,rage at first sexual behavior, marital situation, and income.The risk of high risk sexual behaviors in the single or separated/divorced widowed workers was twice more higher than those of recently married or remarried.Conclusion Construction workers are the key population for the AIDS/STD prevention and control.